Squamous Cell Carcinoma of the Upper Aerodigestive System

Etiology

As outlined previously, the most important risk factors for SCC are alcohol consumption and use of tobacco products, which seem to have a synergistic effect. A recent shift in the primary site distribution within UADT cancers has drawn attention to an important subgroup of cancers associated with infection by oncogenic viruses. The viruses of interest are HR-HPV (subtypes 16, 18, 26, 31, 33, 35, 39, 45, 51, 52, 53, 56, 58, 59, 66, 68, 70, 73, 82), and EBV. EBV has already been mentioned as being associated with NPCs, not only in the undifferentiated and nonkeratinizing tumors but also in keratinizing SCCs. The role of HR-HPV as an oncological agent in UADT SCC was suspected over 2 decades ago. More recently, the site specific incidence of HPV-associated oropharyngeal cancer increased dramatically in developed countries, while those countries oral cavity cancers traditionally associated with alcohol and tobacco/tobacco-like use have remained stable or decreased. The HPV-associated carcinomas are usually nonkeratinizing SCC occurring in the crypts of the tonsillar area (Waldeyer’s ring), as well as in the sinonasal tract. Meta-analyses of epidemiologic studies and multicenter case-control studies have confirmed HPV as an independent risk factor for oropharyngeal cancer, with a range of odds ratios of 3.7 to 5.4. Tonsillar carcinomas appear to have the highest prevalence of HPV, although HPV-associated sinonasal tract, oral cavity, and laryngeal tumors are also known. HPV 16 is the most prevalent HPV type found in 84% of HPV DNA–positive tumors. Interestingly, patients with HPV 16–positive tumors of oropharynx have a better overall and disease-specific survival rate compared with the HPV-negative group. The testing for p16-positive tumors of the oropharynx serves as a surrogate marker for HR-HPV in this anatomic site. Recent data suggest the sinonasal tract as the second most common UADT site with HPV-associated cancers, approximately 20% to 25% have been positive for a variety of HPV subtypes to include 16, 18, 31/33.

Some evidence presented suggests that genetic predisposition also plays a role in the origin of SCC, although it has also been reported that environmental factors may contribute to familial aggregation of SCC. Possibly, it concerns the outcome of interplay between carcinogens and the ability to repair their damage.

Epithelial carcinogenesis is thought to be a multistep process involving the sequential activation of oncogenes and the inactivation of tumor suppressor genes in a clonal population of cells. These genetic and epigenetic changes generate concomitant phenotypic changes in the tumor cells that promote their survival and proliferation. A number of reproducible molecular alterations, some definitively characterized and some inferred, have been identified. Recently, there has been considerable interest and focus regarding the molecular alterations observed in SCC and how they may be related to biology, diagnosis, and treatment. In general, these can be categorized as loss of heterozygosity (LOH)/copy number alterations (CNA), hypermethylation, changes in ribonucleic acid (RNA) molecule expression (messenger [m]RNA and micro [mi]RNA), and DNA mutations.

Where appropriate, this chapter will summarize the currently available data with respect to the molecular changes observed in head and neck malignancies. Where possible, it will also seek to correlate these molecular changes with potential improvements in the areas of diagnosis, prognosis, and prediction.

Loss of heterozygosity occurs when large portions of chromosomes are lost. The repeated loss of a specific chromosomal region is thought to be associated with the presence of a tumor suppressor gene. LOH at 3p and 9p is a common event in both dysplastic oral lesions and SCC. Copy number alterations (CNA) represent another type of genetic abnormality where segments of the genome are lost or gained during cancer development. Copy number gains have been observed in 3q, 6p, 8q, 11q, 16p, and 17q. Conversely, reproducible losses have been observed in 2q, 3p, 4q, 8p, 9p, 11q, and 18q. HR-HPV- and HR-HPV+ SCC have been shown to have similar CNA profiles with certain unique differences. For example, loss of 14q32 and 11q has been observed with far greater frequency in HR-HPV+ tumors. Hypermethylation of gene promoter regions is thought to play a significant role in cell cycle control, DNA damage repair, apoptosis, angiogenesis, invasion, and metastasis. In fact, in certain cancers, there is evidence to suggest that gene silencing is a more common mechanism of gene inactivation than somatic mutations and deletions. Aberrant gene promoter methylation is considered to be an early event in the development of SCC. HPV status-independent association of alcohol and tobacco exposure or prior radiation therapy with promoter methylation of FUSSEL18 , EBF3 , IRX1 , and SEPT9 , but not SLC5A8 , in head and neck SCC. These findings support the contention that, in addition to somatic mutations, promoter methylation of important tumor suppressor genes may play an important role in the mechanism of SCC development. In addition, differences in methylation patterns when comparing HPV+ and HPV- SCC have been reported. Further, methylation patterns have been shown to vary significantly across different anatomic subsites of SCC. Interestingly, global methylation patterns of SCC patients in India were found to be 95% similar to those found in US SCC patients. miRNAs are single-stranded RNA molecules initially described in the nematode Caenorhabditis elegans and are typically 20 to 22 nucleotides in length and play an important role in physiologic and pathologic processes, including apoptosis, development, and differentiation. In general, downregulated miRNAs act as tumor suppressor genes, while upregulated miRNAs typically act as oncogenes. Several hundred different miRNAs have been found to demonstrate aberrant expression in SCC. However, there is considerable variability, which may be caused by the multifactorial etiologies of SCC. For example, HPV-positive SCC miRNA profiles are most similar to cervical cancers than HPV-negative SCC. The development of next-generation sequencing (NGS) platforms, has dramatically improved our understanding of the types and frequencies of genetic alterations observed in cancer. Several large-scale exome sequencing studies have defined the mutational landscape for SCC. A number of important findings have come from these studies. First, several genes previously proposed as playing critical roles in SCC ( TP53, CDKN2A, PIK3CA ) were found to be mutated with sufficient frequencies to support their potential role as drivers in cancer development. Second, a number of novel and potentially targetable genetic alterations were identified, particularly NOTCH1 and its associated pathways and FAT1 . Third, while TP53 was most frequently mutated gene, the mutational frequency for the other most common genes ranged from 1% to 23%, suggesting that there is considerable intertumoral variability with respect to the specific mutations harbored in a given tumor. Finally, the mutations identified in HPV+ and HPV- tumors were different. For example, HPV- tumors often harbored TP53 mutations, CCND1 , PIK3CA , EGFR , and FGFR1 amplifications, and CDKN2A deletions. Conversely, HPV+ tumors typically demonstrated PIK3CA amplifications/deletions and FGFR3 mutations.

Pathologic Features and Prognosis

A UADT SCC is a malignant epithelial tumor with squamous differentiation characterized by the formation of keratin or the presence of intercellular bridges or both. This diagnosis is usually not difficult to make, the most significant diagnostic problem being very marked pseudoepitheliomatous hyperplasia of the mucosa, often overlying a granular cell tumor or an infectious process that may be mistaken for SCC. However, when trying to infer data with prognostic significance from the histology, one enters an area replete with difficulties and uncertainties. In fact, tumor size and stage still represent the most significant prognostic factors for a patient with a UADT SCC, although careful assessment of some additional histomorphologic features appears to have some statistical relevance to the prognosis.

Nevertheless, for more than 80 years, pathologists have been trying to obtain information regarding prognosis by scrutinizing their histologic slides. When briefly reviewing this area, studies aimed at establishing associations between histology and survival as well as between histology and neck node disease are taken into account. Different approaches have been followed to obtain prognostically relevant data from histologic examination. The first attempts were made by Broders. His classification system was based on the proportion of the neoplasm resembling normal squamous epithelium. Although some authors report histologic grade to have prognostic significance, UADT SCC in most instances exhibits a heterogeneous cell population with differences in the degree of differentiation, which may lead to a high degree of intraobserver and interobserver differences in the histologic grading of a tumor. Furthermore, in practice, most UADT SCCs are graded as moderately differentiated, which may explain the poor correlation between patient outcome and histologic grading, based on degree of differentiation. In an extensive multicenter study of more than 3000 patients, it was concluded that grading of UADT SCC, although a common practice, has not evolved as an important factor in treatment planning, this being caused by the modest differences in survival rates between well and poorly differentiated tumors. More recently, a tumor grade is not assigned for HR-HPV–associated tumors of the oropharynx and sinonasal tract.

To obtain a more detailed morphologic evaluation of the growth potential of a UADT SCC, Jakobsson and colleagues developed a multifactorial grading system, thereby paying attention not only to tumor features but also to the relationship of the tumor to the surrounding host tissue. This system has been used for SCC at various locations in the UADT with varying results, as reviewed by Anneroth and colleagues. Some studies indicate that the value of this multifactorial grading system may improve when only the deeply invasive margins of the tumor are evaluated. Tumor features that are assessed in this multifactorial grading system are degree of keratinization, nuclear pleomorphism, and number of mitotic figures. Features related to the tumor-host relationship are pattern of invasion, stage of invasion, and extent of peritumoral lymphoplasmacytic infiltration. Each assessed feature is scored from 1 to 4, and the scores for each morphological feature are added together for a total malignancy score.

Because not all morphological features are necessarily of equal prognostic importance, however, attention also has been paid to the importance of individual histologic parameters. The most important appears to be the pattern of invasion (the advancing tumor border), tumors invading with pushing borders being less aggressive than tumors exhibiting diffuse spread with tiny tentacular strands or single cells ( Fig. 2.3 ). The qualitative growth pattern at the advancing tumor border, particularly the thin stranded type, has been shown to be significantly predictive of locoregional recurrence and disease specific survival. The worse pattern of invasion (WPOI) is a component of the current AJCC staging system. Data on the specific significance of other parameters from the multifactorial grading system are less extensive. A grading system based on the presence or absence of keratin ( Fig. 2.4 ) as the only parameter to distinguish between well-differentiated and poorly differentiated cases was shown to make an independent statistically significant contribution to the prediction of prognosis.

When looking at the peritumoral lymphocytic infiltrate, one study mentions an inverse correlation between extent of infiltrate and incidence of neck node metastasis ; no prognostic significance for this feature was found in other investigations. However, when analyzing the significance of individual cellular components, the number of T lymphocytes appeared to have some relevance. The host’s reaction to an SCC may be visible not only as a peritumoral lymphocytic infiltrate but also as tumor-associated tissue eosinophilia, a feature of uncertain prognostic significance.

Other histologic items that are not included in this multifactorial grading system, but nevertheless are considered to be prognostically important are tumor thickness, are perineural growth ( Fig. 2.5 ) and vascular invasion ( Fig. 2.6 ). The significance of the density of tumor vessels in the stroma adjacent to the tumor is controversial. Concerning perineural invasion, one should be aware of the fact that in and around the oral cavity, intraneural and perineural epithelial structures are present that are not associated with malignant growth but probably are persisting epithelial embryologic structures. Those structures are found at the medial surface of the mandible and are known as the juxtaoral organ of Chievitz, or they may be present in association with intrabony nerves, probably representing odontogenic epithelial nests ( Fig. 2.7 ), as well as in the anterior maxilla, probably representing a nasopalatine duct remnant. The intimate relationship between these islands of epithelium and peripheral nerves could be erroneously interpreted to represent perineural and intraneural invasion.

Aside from the evaluation of the aforementioned tumor features, the pathologist contributes to an additional significant prognostic parameter by evaluating the completeness of the primary excision. Almost all authors who have investigated the significance of tumor at the surgical margins agree that this finding is associated with an increase in local recurrence and mortality. Some authors observed this association only in patients with invasive tumor at the margins ; others found the same negative influence in the event of tumor close to the margins (<5 mm) or with patients having dysplasia or carcinoma in situ at the surgical margins. Probably the negative influence of positive surgical margins is caused, at least partly, by its close association with other tumor factors that have an adverse effect on prognosis, especially T stage. Also, anatomic tumor location and site of the involved margin, mucosal versus deep soft tissue and/or bone, may play a significant role and are worthy of inclusion in the surgical report. In a series of small intraoral cancers, completeness of excision turned out to be the only factor of prognostic relevance, other histologic variables being irrelevant in predicting recurrence at the primary site. In this study, definition of completeness of excision was dependent on tumor features. In the event of invasive growth in tiny nests and strands of tumor cells, the distance between individual tumor nests had to be less than the distance between the resection margin and the tumor nest closest to this margin. Thus if the distance between tumor nests was greater than the margin–tumor distance, resection was considered not to be sufficiently radical, and hence the surgery was tabulated as incomplete. Sometimes, distance between the main tumor and separate nests can be large ( Fig. 2.8 ). This approach for margin analysis was validated in a larger study of almost 400 patients in which it was shown that the recurrence rate in the cases with positive margins was five times higher than in the cases with margins free of tumor or dysplasia, with recurrence at the primary site in cases of free margins being less than 5%.

Intraoperative consultation for assessment of mucosal surface lesions at the surgical borders of a resection can be useful in differentiating inflammatory lesions and/or presence of neoplasia at the surgical margin. The procurement of surgical margins to be evaluated varies by institution: (surgeon procured or pathologist procured), type of tissue submitted (soft tissue, touch preparations of bony margins, curetting of bone marrow) or by specimen-based versus status postexcisional cavity biopsy specimen-based data. A negative surgical margin seen on frozen-section evaluation and confirmed on permanent-section evaluation does not ensure local control of disease but has been shown to enhance local control. The criteria for a positive margin on frozen section is the same as discussed earlier. Others have proposed that the status of margin assessment should include other findings, such as pattern of invasion, perineural invasion, and lack of lymphocytic response to more accurately guide and assess therapeutic intervention.

It is obvious from the foregoing that, when dealing with a UADT SCC specimen, the pathologist should pay attention to all tumor features that may assist the clinician in assessing the need for further treatment. Therefore the pathology report should at least include data on tumor size and thickness, growth pattern at advancing tumor border, perineural and lymphovascular invasive growth, degree of differentiation, and evaluation of the margins, including tumor distance from the margins. SCC arising in the oropharynx should be stained for the HR-HPV surrogate marker at this site, p16+ (at least 70% of nuclei positive). A positive p16 stain at other sites, such as the sinonasal tract, require additional testing for HR-HPV via in situ hybridization or polymerase chain reaction (PCR). If a neck dissection is included, the size, number, site, side relative to the primary tumor, and presence or absence of extranodal spread should be stated because of prognostic significance. A standard reporting form as provided by the Royal College of Pathologists, College of American Pathologists and other international agencies will facilitate computer-based analysis when performing retrospective studies. Such guidelines and minimum data sets will produce reliable standardized data allowing prospective multicenter research projects.

In addition to studying conventional histopathologic aspects that could have prognostic significance, attempts have been made to obtain data with predictive value in other ways. Some authors have tried to obtain more objective data for features also assessed in routine histologic sections. This especially applies to the rate of proliferation or prognostic significance of p53 overexpression. These studies have provided no objective evidence of any association with patient outcome.

The value of molecular markers in determining the prognosis for individual cases has not yet been demonstrated; consequently, none of the markers has gained any significance for daily practice to date. However, a number of different types of molecular alterations may hold future promise in the diagnostic setting. For example, LOH at several regions (2q, 3p, 4q, 6q25-27, 8p, 8p21.2, 8p23, 9p21-22, 10q, 11q23, 13q, 14q, 17p, and 18q) has been associated with poor prognosis, including increased risk of recurrence and decreased survival from SCC. Similarly, CNA may have prognostic value in predicting SCC recurrence, metastatic disease, and/or decreased overall survival. Furthermore, several studies have suggested that gene promoter methylation may be of value both predictively and prognostically. For example, different methylation patterns is associated with a number of pathologic features, including lymph node metastasis (CDKN2A, DAPK1, MGMT, MLH1) , treatment response (CHD1, DAPK1, NEFL, TIMP3) , progression-free survival (CCNA1, MGMT, GAL, GALR1, TAC, TACR1, TIMP3) , and overall survival (CDH1, CDKN2A, CSPG4, DCC, MGMT, MINT31) . Finally, detection of hypermethylated DNA for a subset of genes (DAPK, DCC, MINT-31, TIMP-3, p16, MGMT, CCNA1) in saliva samples may be predictive for local recurrence and overall survival. In addition, mRNA expression profiling studies have been performed on oral SCC. Importantly, a number of these have investigated the diagnostic utility of expression profiling in terms of T stage, depth of invasion, recurrence-free survival, cervical lymph node metastases, progression and survival. In addition, expression profiling has also been used to stratify tumors based upon different etiologies, including HR-HPV+ versus HR-HPV-, smoker versus nonsmoker, and smoker versus betel quid user.

A number of studies have investigated the role of miRNA panels in the diagnostic arena. For example, a 21-miRNA panel may be able to differentiate between normal oral mucosa and OCSCC. Similarly, differential expression of serum miR-16, let-7b, miR-338-3p, miR-223, and miR-29a may be a useful biomarker for identifying patients with SCC. Finally, increased expression of miR-96 and decreased expression of miR-16, miR-125a, and miR-184 at the surgical margins of recurrent lesions. miRNA expression profiles are also being investigated for their prognostic utility and have been reported to correlate with certain clinical features, including clinical stage, metastasis, and survival. For example, expression of miR-21 has been associated with advanced clinical stage, nodal disease, and survival. In addition, altered expression of a number of other miRNAs, including let-7, miR-31, miR-17, miR-125b, miR-155, miR-181, miR-205, miR-375, and miR-491 have been found to be associated with poor survival. Peng et al. evaluated the expression of 760 miRNAs for prognostic significance in OCSCC. They found that differential expression of miRNA-218, miRNA-125b, and let-7g held prognostic significance with disease-free survival, suggesting that reduced expression of the miRNAs may improve prognostic stratification. Ganci et al. determined that increased expression of miRNA-21-3p, miRNA-96-5p, miRNA-141-3p, and miRNA-130-3p were associated with shorter recurrence-free survival. Wong et al. used the TCGA data to identify a set of prognostic biomarkers of OPSCC and OCSCC. They identified increased expression of miRNA-193b-3pj and miRNA-455-5p as being positively associated with OPSCC survival and miRNA-92a-39 and miRNA-497-5p as being negatively associated with OPSCC survival. Importantly, this model was able to further stratify HR-HPV+ patients into low-risk and high-risk cohorts. This is an important observation. In general, HR-HPV+ patients have a better prognosis. However, there is growing appreciation of survival heterogeneity among HR-HPV+ patients. Therefore further validation of the risk stratification by Wong and colleagues may provide us with improved prognostic capabilities and treatment options for HR-HPV+ patients. Scapoli et al. further identified an association with progression and metastasis in OCSCC and the downregulation of miRNA-155, miRNA-146a, and let-7i Li et al. demonstrated that upregulation of miR-21 was positively correlated with advanced clinical stage, lymph node metastasis, and decreased overall survival. A panel of 12 miRNAs has also been identified that are independent prognosticators of recurrence-free survival and four miRNAs that correlate with cancer-specific survival. There is also evidence that changes in miRNA expression patterns may correlate with resistance to therapy. For example, Dai et al. reported that upregulation of miR-101, miR-181a, miR-181d, and miR-195, combined with the downregulation of miR-100, miR-130a, and miR-197 was consistent with resistance to chemotherapy. Similarly, Sun et al. found that decreased expression of miR-15b and miR-200b was associated with radioresistance. Finally, chemoradioresistance has been associated with increased expression of miR-196a.

There are a number of publications that have sought to identify classes or panels of somatic mutations that may have prognostic and diagnostic utility in SCC. For example, targeted next-generation sequencing of locally advanced HR-HPV+ and HR-HPV- SCC found that activating mutations in PIK3CA , KRAS , NRAS , and HRAS identified a subgroup of patients with HR-HPV+ SCC that are associated with reduced overall survival after adjuvant chemoradiation. In addition, mutational landscape of recurrent and metastatic SCC demonstrated distinct mutational profiles between the two groups. These findings suggest that the molecular landscape of recurrent and metastatic SCC can be quite variable and this may influence how one approaches treatment in the advanced stage/recurrent setting. In addition, a mutation-based signature of 10 genes ( HRAS , BRAF , FGFR3 , SMAD4 , KIT , PTEN , NOTCH1 , AKT1 , CTNNB1 , and PTPN11 ) was found to be an independent predictor of decreased disease-free survival. Similarly, the combination of TP53 mutation and loss of chromosome 3p was found to be associated with a significantly decreased survival time.

Etiology

The etiology of NPC is a multifactorial interaction of race, genetics, environment, and EBV. Reports of familial clusters suggest a genetic component. Dietary factors have been proposed. The annual incidence in North America is 0.3 to 0.7 cases per 100,000 versus that of Southern China, 15 to 50 cases per 100,000. Persons in Southeast China who eat nitrosamine-rich salted fish (Chinese style) have one of the highest incidences of NPC, particularly the seafaring Tankas, for whom salted fish is a prominent dietary component. The dietary factors, however, have not explained the male-to-female ratio of 3:1 (which is seen in both endemic and nonendemic areas), or the ubiquitous association with EBV.

The presence of EBV within the epithelial cells and not the lymphoid infiltrate has been demonstrated by various methodologies, including karyotyping, electron microscopy, polymerase chain reaction, and immunohistochemistry, but most reliably by in situ hybridization RNA, Epstein-Barr virus–encoded small RNA (EBER). High titers of immunoglobulin A antibodies to EBV-specific antigens, viral capsid antigen, and early antigen have been reported to correlate with tumor burden, relapse, and clinical progression.

Clinical Features

NPC occurs in all age groups, most commonly in those 40- to 60-years-old. It is most common in males, by a 3:1 ratio, in contrast to SCC of other head and neck sites, which have an even higher male incidence of 7:1. In some intermediate- and low-risk areas, there is a bimodal age distribution, with peaks in the second and sixth decades. In the United States among blacks, the tumor has been reported to peak at 10 to 19 years of age. In areas of Africa, NPC accounts for approximately 10% to 20% of childhood malignancies, and in the Sudan, it is the most common pediatric cancer. In the high incidence region of Southern China, however, NPC is only rarely seen in children.

The most common site of origin of NPC is on the lateral wall at the Rosenmüller fossa. Patients may present with a variety of symptoms: serous otitis media, nasal obstruction, tinnitus, facial numbness, epistaxis, or cervical adenopathy commonly seen in the apex of the posterior cervical triangle (level 5, see Chapter 11 for description of levels). The majority of patients (60%–72%) will present with unilateral or bilateral cervical adenopathy. The site of the primary tumor may be occult.

More advanced disease is usually present if the patient’s symptoms include hearing loss, palatal paralysis, otalgia, headache, or evidence of cranial nerve involvement (10%–12% of cases). The cranial nerve involvement is easily explained by the proximity of the nasopharynx to the foramen lacerum and the contents of the most commonly involved region in NPC extension, the paranasopharyngeal space, which contains branches of the trigeminal nerve ( Fig. 2.9 ). In one computed tomography study of 262 patients with NPC, cranial nerve palsy of the third through the sixth cranial nerves had evidence of erosion of the base of the skull; however, erosion of the base of skull did not imply cranial nerve involvement. Other presentations or evidence of relapse of tumor may be paraneoplastic syndromes, such as hypertrophic osteoarthropathy syndrome (Pierre Marie’s syndrome), leukemoid reaction, and fever of unknown origin.

One of the notable clinical features of NPC is the propensity for distant metastasis. At the time of presentation, 5% to 11% of patients have distant metastases. During the course of the disease, 50% to 60% of patients develop distant metastases. Autopsy series report the overall metastasis incidence to be 87%, with the common sites being bone, lung, liver, and distant lymph nodes. The natural history of disease progression is short, with 78% of metastases occurring within 18 months of the first symptoms. After detection of systemic metastases, median survival is only approximately 6 months. The frequency of distant metastatic sites for NPC as compared with those of other UADT SCCs is the following: bone (65% vs. 25% UADT SCC), liver (29% vs. 23% UADT SCC), and lung (18% vs. 84% UADT SCC). Approximately 25% of patients with evidence of metastatic disease will have involvement of the bone marrow.

A number of different staging systems for NPC have been developed in different parts of the world. The most recent tumor-node-metastasis (TNM) classification by the AJCC is customized for the unique behavior and therapeutic needs for NPC. The original staging system proposed by Ho, developed in an area with one of the highest incidences of NPC, underwent modification, which has reduced the number of stages without reducing the accuracy of predicting prognosis. Some advocate that the modified classification of this system shows a more even distribution of patients among stages, with a greater power of predicting prognosis, than other classification systems. Unfortunately, there has not been one single generally accepted classification for comparison of treatments of NPC between centers, although the most recent AJCC staging is gaining acceptance.

A subset of NPC reports from the United Kingdom and United States, nonendemic areas of EBV-associated NPC, have reported HR-HPV–associated NPC. The cases have a strong predilection for Caucasians and are rare in Eastern Asian populations. The biology of these HR-HPV NPC tumors is still to be understood.

Pathologic Features

NPC accounts for 3.7% of UADT tumors. All forms of NPC are derived from the surface epithelium of the nasopharynx, having ultrastructural features, such as tonofilaments and desmosomes of SCC. Tumors with glandular differentiation do not form part of the histologic spectrum of NPCs.

The current World Health Organization (WHO) classification has retained previous changes, which included the addition of a new category of basaloid SCC (BSCC). When comparing the current revisions of the WHO classification with the original one, there are significant alterations. The fourth edition of the WHO histologic typing of UADT tumors again divides NPC into three broad histologic types: keratinizing SCCs, nonkeratinizing carcinomas, and BSCC, as shown in Table 2.1 . NPC stains positive for p63, p40, pan cytokeratins, patchy expression for low-molecular-weight cytokeratins, such as epithelial membrane antigen (EMA), CK20 and CK7 are negative. The nonkeratinizing type of NPC is associated with a positive EBV serology, marked propensity for cervical lymph node metastasis, and radiosensitivity. Irrespective of their histologic subtypes, almost 100% of cases of NPC have demonstrable EBER in the nuclei of their tumor cells, as demonstrated by in situ hybridization EBER-1. The positive hybridization signal in keratinizing NPC, however, is less in proportion to that of malignant cells, usually limited to basal cells, than in other histologic types of NPC.

Keratinizing NPC exhibits the features of a conventional SCC as occurs anywhere in the UADT. These keratinizing tumors: (1) are infrequently seen in high-incidence areas (<5%), (2) represent one-fourth to one-half of NPCs in low-incidence populations, (3) are more often associated with locally advanced disease and lower propensity for lymph node or distant metastases, (4) are usually not radiosensitive, (5) occur primarily in adults, and (6) have been associated with cigarette smoking.

The nonkeratinizing carcinoma group is no longer subclassified into differentiated and undifferentiated subtypes. These two subclassified groups have overlapping histologic features and similar epidemiologic and biological characteristics (frequent lymph node involvement and distant metastases) rendering the subclassification of no clinical or prognostic value. NPC, nonkeratinizing, consists of cells in which squamous differentiation is not evident on light microscopy; these cells have distinct margins and usually form plexiform masses or, rarely, papillary structures (histomorphology previously classified as differentiated type). Some find this pavement-like arrangement of cells with well-defined borders reminiscent of urothelial transitional cell carcinoma, and thus this type of NPC may mimic nonkeratinizing SCC occurring in the sinonasal cavities and discussed under that heading.

Less-differentiated NPC, nonkeratinizing type (previously classified as undifferentiated carcinoma) consists of cells with scant cytoplasm, oval or round vesicular nuclei, and prominent nucleoli. The cell margins are indistinct, imparting a characteristic syncytial growth pattern, and the cells may be arranged in irregular masses or as loosely connected cells in a lymphoid stroma. When associated with a lymphoid stroma, these tumors have been referred to as the lymphoepithelial carcinoma or as lymphoepithelioma , a term now reserved for anatomic locations other than the nasopharynx.

The nasopharynx contains tonsillar tissue and therefore, not surprisingly, there are also reported cases of HR-HPV–associated NPC. These cases mentioned earlier have been reported primarily from nonendemic areas for EBV-associated NPC. HR-HPV is most often reported in differentiated and undifferentiated nonkeratinizing types of NPC. Currently, it is recommended that NPC that is negative for EBV be tested for HR-HPV and the possibility of direct extension from a primary oropharynx carcinoma be excluded.

Molecular Features

As discussed earlier, EBV is the major causal agent for the development of NPC. Several EBV-associated proteins, including Epstein-Barr nuclear antigen 1 (EBNA1) and latent membrane proteins (LMP-1, 2, 3), play a critical role in altering signaling pathways associated with proliferation/cell cycle, as well as inhibition of apoptosis. Interrogation of the NPC genomic landscape has identified a number of significantly mutated genes, including BAP1 , MLL2 , TSHZ3 , TP53 , PIK3CA , ERBB3 , ERBB2 , KRAS , and NRAS . In addition, gene expression profiling has identified 137 differentially expressed genes, 13 of which were able to subclassify patients into low- and high-risk for the development of distant metastasis in patients with locoregionally advanced NPC. Similarly, microRNA profiles have been characterized and some of these, including miR-142, miR-26a, miR141 and let-71, may also be able to prognostically stratify patients into low- and high-risk categories for the development of distant metastasis. Finally, oncogenic amplifications of a number of genes have been identified through genome-wide array-based comparative genomic hybridization.

Differential Diagnosis

Keratinizing NPC should not give origin to differential diagnostic problems other than for SCC at other UADT sites. Nonkeratinizing NPC, differentiated subtype may resemble, as already mentioned, nonkeratinizing SCC of the paranasal sinuses; however demonstration of EBV within the tumors confirms the EBV-NPC. Further details on the differential diagnosis of the less differentiated nonkeratinizing NPC are mentioned when lymphoepithelial carcinoma is discussed.

Treatment and Prognosis

For treatment of EBV-NPC, irradiation is usually the first choice. The survival of NPC patients is influenced by age, sex, T and N stage, and histologic type; the nonkeratinizing NPC is far more radiosensitive than keratinizing SCC. For patients treated with radiotherapy, 5- and 10-year survival rates have been reported to be 58% and 47%, respectively. The treatment modality for NPC is based on the histological type, keratinizing versus nonkeratinizing carcinoma. The nonkeratinizing histological types are radiosensitive. External beam–supervoltage radiotherapy is the standard treatment of locoregionally confined NPC. The keratinizing types of NPC have a poor response to irradiation and are, therefore, more amenable to surgical resection. Although improvements in radiation technique have occurred, both local control and distant failure remain problems. Neoadjuvant chemotherapy studies have shown NPC to be sensitive to preirradiation chemotherapy.

Several features have prognostic significance in NPC although the most important prognostic factor is stage at presentation. Those features associated with a favorable outcome are: (1) female gender, (2) age younger than 40 years at onset, and (3) nonkeratinizing NPC histology. Those features associated with an unfavorable prognosis are: (1) symptoms for more than 1 year, (2) keratinizing carcinoma histology, (3) positive lymph nodes with fixation in the lower neck, (4) cranial nerve involvement, and (5) distant metastases. Those features not appearing to have an impact on prognosis are: (1) unilateral or bilateral lymph nodes in the upper neck and (2) involvement of bone at the skull base. Tumor volume has also been shown to have prognostic significance.

The prognostic significance of HR-HPV in NPC has yet to be established.

Clinical Features

Malignancy of the sinonasal region represents 0.2% to 0.8% of all malignancies and approximately 3% of all those of the UADT. In contrast to other locations, SCC represents approximately 70% of the malignancies in the sinonasal region. The distribution of carcinoma by anatomical site is the maxillary sinus (55%–60%), nasal cavity (19%–35%), ethmoid sinus (9%–15%), nasal vestibule (4%), and frontal and sphenoid sinuses (1% each).

The majority of the tumors in this region present in a late stage (T3 and T4), as the initial presenting signs are nonspecific. The lacking specific clinical symptoms were noted to delay diagnoses from 3 to 14 months in one series. Extent of tumor at the time of diagnosis best correlates with prognosis rather than degree of differentiation, with the exception of anaplastic carcinoma.

Regional metastases from sinonasal neoplasms are uncommon (9%–14% for SCC). Metastasis from these tumors usually implies soft-tissue extension (antral tumors: cheek and soft palate; ethmoid tumors: medial canthal skin and nasopharyngeal extension). The maxillary sinus drains primarily to the submandibular nodes. The lymphatic drainage of the ethmoid labyrinth is to the superior cervical nodes, and some drain directly posteriorly to the retropharyngeal nodes. With advances in imaging, assessment of retropharyngeal lymph nodes is possible.

Although site-specific systems have been proposed, the only internationally recognized staging system is for maxillary and ethmoid tumors. In 1938 Ohngren proposed a theoretical plane from the medial canthus of the eye to the angle of the mandible, which created an anteroinferior (infrastructure) and a posterosuperior (suprastructure) to the maxillary sinus area. This hypothetical division has clinical relevance because the infrastructure tumors present early, therefore good prognosis, whereas the suprastructure tumors usually present after extensive tumor growth has occurred. The American Joint Committee on Cancer has adopted a T classification for the maxillary sinus and nasoethmoidal complex, as noted in Appendix.

Pathologic Features

In the histologic classification of the nasal cavity and paranasal sinuses, there has historically been some confusing and controversial terminology. The majority (>70%) of the carcinomas in this region are keratinizing SCCs, defined as a malignant epithelial neoplasm arising from the surface epithelial lining and exhibiting squamous differentiation. Most of the controversial terminology revolves around nonkeratinizing SCCs. The synonyms for nonkeratinizing carcinoma have included cylindrical cell carcinoma (Ringertz squamous carcinoma), transitional cell carcinoma, and schneiderian carcinoma. Reference to cylindrical cell carcinoma can be found in the literature around 1900 as a histologic type of nasal carcinoma, but it was fully described by Ringertz in 1938. The histologic description rendered by Ringertz described a sometimes papillary nonkeratinizing epithelial tumor that invaginated into the stroma. The invaginating epithelial growths had a palisading basal layer forming a crisp demarcation at the epithelium-stroma interface and forming a ribbon or garland-like pattern with central zones of necrosis. In the American literature more than a decade earlier, Quick and Cutler introduced the James Ewing term transitional cell carcinoma for a category of upper airway tumors that “exhibited transitional epithelial characteristics with cylindrical or cuboidal cells free of keratosis.” This term referred to poorly differentiated carcinomas originating from the schneiderian membrane and was never clearly defined as an entity. The term transitional carcinoma was used by later investigators to describe malignant transformation in transitional papillomas of the nasal cavity. Transitional was chosen because of the histologic resemblance of the malignant epithelium to that of transitional epithelium of the urogenital tract. Also, articles may be found that equate all three terms: transitional, schneiderian, and cylindrical cell carcinomas .

Some authors use these designations to denote lesions also categorized as nonkeratinizing SCC of the nasal cavity and paranasal sinuses or consider them to be just a subtype of SCC ; others use the term cylindrical cell carcinoma to identify a variant of sinonasal SCC that may exhibit intracellular mucin production and sometimes has a growth pattern similar to a papilloma, making stromal invasion not immediately apparent. To end this discussion on semantics and nosology, we advocate use of the WHO approach, recognizing cylindrical cell carcinoma as one of the synonyms of sinonasal nonkeratinizing SCC and recognizable by features as originally outlined by Ringertz: a papillary lesion composed of invaginating ribbons of pleomorphic nonkeratinizing cells that are mainly cylindrical and often arranged perpendicularly to the underlying basement membrane.

The lesion invades with a pushing border, which makes stromal infiltration not immediately apparent when one is evaluating small biopsy specimens ( Fig. 2.11 ). The tumor may exhibit squamous metaplasia, which, if extensive, makes cylindrical cell carcinoma indistinguishable from conventional SCC (see Table 2.1 ). The current WHO classification recognizes cylindrical cell carcinoma, transitional cell carcinoma, and Schneiderian carcinoma as synonyms for nonkeratinizing SCC.

As mentioned previously, the correct classification of these tumors is complicated, as histologic examination, immunohistochemical staining, and molecular analysis are needed to classify the tumor. The classification is important for prognosis and therapeutic decision making. Two such entities occur in the sinonasal tract: chromosomal translocation t(15;19) NUT-BRD4 in NUT carcinoma and HR-HPV–related multiphenotypic sinonasal carcinoma (presence of p16+ and HR-HPV and negative for t (6;9) MYB-NFIB rearrangement).

Another small number of recently described carcinoma of the sinonasal tract displays absence of SMARCB1 (INI1), a protein encoded by the SMARCB1 tumor-suppressor gene. This oncogene is implicated in a growing number of malignancies in many different anatomic sites, CNS, kidney, and soft tissues.

Molecular Features

Recently described in a series of a variety of sinonasal undifferentiated and poorly differentiated carcinomas is the identification of frequent IDH2 R172 mutations. IDH2 mutation may an actionable site for targeted therapy in these unique and diverse carcinomas.

Differential Diagnosis

Nonkeratinizing SCC (cylindrical cell type), should not be confused with papillary SCC (PSCC), a lesion discussed more extensively in the section devoted to specific variants of SCC. Distinctive features are the lack of cylindrical cells in PSCC and the presence of papillary protrusions covered with an epithelial lining with the features of carcinoma in situ. Moreover, the histology of cylindrical cell carcinoma may mimic that of inverted papilloma. However, the presence of numerous microcysts in the multilayered epithelial ribbons in some parts of the material is valuable in confirming the diagnosis of inverted papilloma, whereas their absence in conjunction with cellular atypia should cause concern that the diagnosis might be SCC.

Treatment and Prognosis

For patients with carcinoma of the sinonasal area, the probability of surviving for 5 years is approximately 50%. Within the nasal cavity, malignancy of the nasal vestibule and septum has a better prognosis, perhaps because of earlier diagnosis, than in the remainder of the nasal cavity and paranasal sinuses. For patients with antral and ethmoidal disease, the probability of surviving 5 years is 48% and 68%, respectively. The 5-year survival rate for patients with T2, T3, and T4 cancers of the antrum is 73%, 41%, and 15%, respectively. There does not appear to be a significant correlation of survival rates with the patient’s sex or age at time of presentation. Although multimodality therapy does not seem to change the 5-year survival rate, it appears to have improved the local control of tumor. Factors limiting patient survival time are related to local recurrence, nodal metastasis, soft-tissue extension to the palate or nasopharynx, proptosis, and orbital symptoms, as metastases account for approximately 10% of deaths.

Treatment and Prognosis

Treatment for the hypopharynx is the combined use of radiation and surgery. The majority of lesions involve the pyriform sinus, and combined therapy is recommended, with the exception of T1 and T2 lesions (single-modality therapy). In one large study of tumors of the pyriform sinus, the overall 5-year disease-free survival rate for combined therapy was 65.2%. A decrease in survival rate after 2 years is primarily caused by distant metastasis and to second primary malignancies. The value of adjunctive chemotherapy in pyriform sinus malignancy is still unclear.

Clinical Features

In discussing the spread of laryngeal carcinoma, it should be noted that traditionally the tumors have been divided by site: supraglottic, glottic, transglottic, and subglottic. The supraglottic tumors involve the false vocal cord, the ventricle, and the epiglottis (laryngeal or lingual aspects) and represent approximately 30% to 35% of laryngeal tumors. These tumors have a marked propensity to spread to the preepiglottic space primarily through fenestrations within the epiglottic cartilage. Approximately 1% of these supraglottic tumors invade the glottis. Invasion of cartilage is exceedingly rare, restricted only to those cases in which the cartilage has undergone osseous metaplasia. The incidence of lymph node metastasis averages approximately 40%. The tumors are primarily treated by irradiation or laryngectomy.

Tumors of the glottic area are the most frequent, accounting for approximately 60% to 65% of laryngeal carcinomas. Glottic tumors arise from the true vocal cords, primarily from the anterior third of the vocal cord, and frequently produce hoarseness. Because of early symptoms, tumors of the glottis may be found in an early stage. Five-year disease-free rates for T1 carcinomas (localized to the vocal cord) have been reported as high as 90%. The degree of anterior commissure involvement appears to have prognostic significance, with patients with a progressively heavier involvement of the anterior commissure subsite having a progressively worse outcome. The incidence of lymph node metastasis in T1 through T4 tumors is 1.9%, 16.7%, 25%, and 65%, respectively. Lesions of the glottis tend to be localized for an extended period of time, primarily caused by paucity of lymphatic vessels within Reinke’s space and the cartilaginous walls. Early cases are usually treated by irradiation. Surgical management can be used to salvage irradiation failures.

The concept of a transglottic lesion was first presented in 1961 by McGavran and colleagues. The term transglottic does not refer to an anatomic site within the larynx but to a pattern of glottic tumor spread that crossed the laryngeal ventricle, therefore involving the supraglottis and glottis, and also with paraglottic space involvement. This particular pattern of involvement appeared to have an aggressive clinical course with a high incidence of lymph node metastasis (52%). Transglottic carcinomas are treated primarily by laryngectomy and lymph node dissections. They represent less than 5% of all cases of laryngeal carcinoma. With time and imprecise use, there has been deviation from the original 1961 concept of transglottic tumor (supraglottic/glottic, as well as glottic/infraglottic). Therefore it is better to specify tumor extension by recording the defined anatomical subsites involved and refrain from the term transglottic.

The infraglottic or subglottic tumors are also rare, representing less than 5% of all the cases. Tumors included in this category are tumors that involve the region between the lower edge of the true vocal cord (where the squamous epithelium ends) and the first tracheal cartilage or extending 1 cm below the edge of the true cord. Other investigators have defined the subglottis as extending from the lower boundary of the glottis to the lower margin of the cricoid cartilage. The tumors in this area frequently show extension into the trachea. Metastasis to cervical lymph nodes is approximately 15% to 20%, and the involvement of paratracheal lymph nodes is approximately 50%. Subglottic tumors are treated primarily by surgical excision and neck dissection, including the paratracheal lymph nodes.

The primary staging scheme for laryngeal carcinomas is clinical staging with pathologic staging representing valuable additional information. Several suggestions for alteration of the TNM classification system have been proposed. It has been argued that there are embryologic, anatomic, functional, and oncologic reasons to divide the larynx into two main areas only, the supraglottis and the glottis (vocal folds), without any further subsites, and to abandon a separate group of subglottic tumors. Finally, the N status should include number, size, site of metastasis, and presence of nodal (ENE) extension.

Treatment and Prognosis

Laryngeal cancer is one of oncologic diseases over the 5-year survival rate has decreased over the past 40 years (66% to 63%). The incidence of laryngeal cancer however is decreasing as tobacco and alcohol consumption changes. In addition to the inverse relationship of primary tumor size with prognosis, lymph node metastasis is another extremely important prognostic factor in laryngeal cancer. Both cervical metastasis and disease-free survival rates have been shown to be related to depth of invasion; for tumors with a thickness of 3.25 mm or greater, an elective neck dissection is recommended.

In advanced laryngeal carcinoma, cervical metastasis has been shown to be the most important prognostic variable for survival. A study with 159 patients (supraglottic, 97 patients; glottic, 60 patients; and subglottic, 2 patients) found disease-free survival rates to be 87% in patients with no regional metastasis, 82% in patients with one to two positive lymph nodes, and 33% in patients with three or more positive lymph nodes ( P < 0.001). Risk of distant metastasis was 5% in node-negative patients and 36% in node-positive patients. Patients with three or more positive lymph nodes had decreased survival rates (at 48 months for node-negative patients, 68%; for patients with one to two nodes, 62%; and for patients with three or more nodes, 20%). Distant metastasis was found to be more common in patients with involvement of lower jugular and supraclavicular lymph nodes.

Extranodal extension (ENE) of carcinoma has significant impact on survival, a factor that is still ignored in the TNM staging, which does not include this issue as a separate item worthy of being recorded. In one series of patients, extranodal extension was present in 31% of N1 nodes and the 5-year survival rate of patients without ENE was 76%, whereas for patients with nodal metastases showing this phenomenon, it was only 17%. The presence of ENE, no matter the size of the lymph node, should be included in the surgical pathology report. The prognostic significance of micrometastases is still being assessed.

Differential Diagnosis

One of the more problematic areas of diagnosis in the larynx is the evaluation of postirradiation persistence of SCC. Often dysplasia or atypia may be limited to the mucosa. Owing to the difficulty in distinguishing between tumor recurrence and postirradiation atypia, most pathologists would prefer to err on the side of conservatism. Pseudomalignant tissue reactions are well documented after irradiation or chemoradiation therapy. Full-thickness mucosal atypia that is histologically identical to dysplasia or carcinoma in situ may be observed. The distinction between benign and malignant can be very difficult with the diagnosis of malignancy based on stromal invasion. The histology of these radiation-induced lesions may show increased mitotic activity and even atypical mitotic figures. Grossly, the growths may be flat or broad-based polypoid lesions with ulceration and radiating vascular connective tissue. An indistinct border between the pleomorphic stromal cells and pleomorphic endothelial cells is a useful finding in radiation-induced atypia. The tinctorial quality of the cytoplasm may be gray-blue on hematoxylin-eosin–stained sections. Immunohistochemistry and flow cytometry findings are nonspecific. When the examiner is trying to make the distinction between recurrent tumor and tissue reaction, finding low-power granulation tissue architecture and similar degrees of cytologic atypia in both the endothelial cells and stroma aid in establishing the benign nature of the lesion.

Early cancer of the larynx is a term that has been used to describe malignant lesions limited to the mucosa similar to a variety of other sites, including the stomach, esophagus, cervix, and so on. The early cancers of the larynx are usually located in the glottis. Unfortunately, the term has been used by clinicians and pathologists to convey different ideas. The clinical definition of early glottic cancer implies a Tcis or T1 lesion, with full chordal motility and no risk of neck metastasis. The pathologic definition describes a microscopically invasive carcinoma that transgresses the basement membrane but is confined to the lamina propria and has metastatic potential. The pathologic description does not include extension into adjacent muscle or cartilage. Mucosal lesions of the glottis composed of carcinoma in situ with a microscopic focus of invasion or a superficial extending carcinoma (SEC; confined to the lamina propria) represent early glottic cancer. Biologically, invasion is present, as is the potential for metastasis.