Extramucosal Diseases of the Head and Neck

Branchial Cleft Cyst

First branchial cleft cysts (BCCs) classically occur in the parotid gland ( Box 14-2 ) or around the external auditory canal (EAC). Several classifications of first BCCs have been developed including Arnot type I (intraparotid cyst) and Arnot type II (cyst in the anterior neck that may drain with a tract through the deep portion of the parotid gland to the EAC; Figs. 14-3 and 14-4 ). Work type I first BCCs are anterior and inferior to the pinna and may communicate with skin anterior and medial to the EAC in the preauricular zone. Work type II BCCs are more common, arise at the angle of the mandible (where we typically see second BCCs), and extend to the junction of the bony and cartilaginous EAC. They may rarely drain into the EAC. Both types of first BCCs may be intimately associated with the facial nerve which gives the ear, nose, and throat (ENT) surgeons fits. Because second BCCs are so much more common, they probably outnumber first BCCs even in the periparotid location ( Table 14-2 ).

Although these lesions usually have fluid density and intensity characteristics, if infected or traumatized, their appearance may be a bit more complex (see Fig. 14-3 ). Adjacent inflammation may be present, and the whole complex may simulate an infiltrative process. Fistulization to the bone-cartilage junction of the external ear may occur with first branchial cleft anomalies.

Venous Vascular Malformations

Venous vascular malformations (formerly inaccurately called hemangiomas because they are not tumors) may occur in the submandibular space as well as in other spaces of the head and neck. On CT, they may show phlebolithic calcification in their later stage (as opposed to monolithic ossification of the Stone Age), but invariably one identifies a lobulated, heterogeneously enhancing mass. Areas of enhancement that are as extensive/intensive as that of the neighboring jugular vein are not unusual. If you perform a fine-needle aspiration (FNA) of this lesion you will be faced with the bane of the aspirator’s existence—recurrent samples of “nothing but blood.” You will be doing the study in vein (Ha! Pun-ishment again!). Do not bother. Interestingly enough, there is a 20% coincidence rate of developmental venous anomalies (venous angiomas) of the brain in those subjects with head and neck venous malformations.

Calculous Disease

By our estimation, calculous disease (in the nonmathematical sense) is the most common benign condition to affect the salivary glands by a factor of the (π ³ !3) ⁴ . Because the submandibular gland secretes a more mucinous, viscous, alkaline saliva and the wider duct must drain in an uphill direction with greater possibility of stasis, calculi occur most commonly in the Wharton duct ( Fig. 14-5 ). In fact, submandibular gland calculi outnumber those in the parotid gland by a “calculation” of four to one. Sublingual gland calculi and minor salivary gland calculi are extremely uncommon. Although most of the calculi associated with the salivary glands are radiopaque, a small percentage of calculi (20%) may not be so radiodense as to be visible on plain films. Viva La CT!

Patients who have calculous disease usually have painful glands, exacerbated by chewing foods that precipitate salivation. If the clinician suspects calculous disease, the usual work-up includes plain films to evaluate for large radiopaque calculi. If no calculi are identified by plain films, or if the patient has a fever associated with a painful salivary gland and an abscess is suspected, CT should be done because it is more sensitive for the detection of calcification and inflammatory masses ( Fig. 14-6 ). This may be one of the rare indications for unenhanced (to see a small calculus and distinguish it from a vessel) and enhanced (to look for signs of inflammation/abscess) CT examinations of the neck. Remember that magnetic resonance (MR) imaging is less sensitive to calcified or noncalcified tiny calculi; larger calculi can be seen as low-intensity areas on T2-weighted scans but flow voids of vessels may simulate calculi.

Calcifications of the parotid glands are also associated with human immunodeficiency virus (HIV) infection, chronic kidney disease, alcoholism, elevated alkaline phosphatase, and autoimmune disease, including sarcoidosis and systemic lupus erythematosus.

In the instance of a calculus that is not radiopaque on CT, one might be forced to perform conventional sialography (cannulation of the salivary duct with injection of contrast). MR sialography can employ either a single shot fast spin echo heavily T2-weighted sequence that highlights the ducts alone or a high-resolution three-dimensional fast spin echo or constructive interference in steady state (CISS) T2-weighted sequence. Sialography is useful in demonstrating strictures of the ducts after passage of a calculus and intraluminal filling defects from nonopaque stones. The sialogram suggests the diagnosis of autoimmune/chronic sialadenitis if there are pruned, truncated main ducts with punctate/globular collections peripherally in the glandular parenchyma.

Treatment of sialolithiasis (a catchy seven-syllable word for salivary gland stones) generally consists of supplying sour solutions to stimulate salivation to spew said stone (say that 10 times fast without spitting!). Transoral resection and sialodochoplasty can be performed for isolated distal duct (close to ampulla) sialoliths. For proximal or glandular stones, the surgeon may decide to treat the patient with resection of the gland. This is often the preferred treatment with recurrent bouts of sialolithiasis with disruptive sialadenitis. A cervical (submandibular) approach may be taken with sialoliths that extend beyond the mylohyoid (in the proximal duct).

Sialosis

Sialosis is a painless enlargement of the parotid glands that has been associated with numerous causes, including (1) diabetes, (2) alcoholism, (3) hypothyroidism, (4) medications including phenothiazines and some diuretics, (5) obesity, (6) starvation, (7) radiation, and (8) the dreaded “idiopathic” causes. This usually is a bilateral and symmetric process that may resolve when the underlying cause has been removed. It should be noted, however, that the normal range of parotid gland size and consistency is varied and often it is difficult to state definitively that the glands are larger than normal. On imaging studies the glands with sialosis generally have a CT density and signal intensity on T2-weighted imaging (T2WI) slightly greater than that of normal fatty parotid glands. The glands in sialosis usually are not as bright on T2WI as glands that are infected. You may see distortion of the facial contour by the enlarged glandular tissue.

Sialadenitis

Sialadenitis refers to glandular inflammation, whereas sialectasis refers to dilatation of ductal spaces. Sialadenitis is often associated with sialectasis. The most common cause of these conditions is calculous disease. The inflamed gland is enlarged and hyperenhancing on CT and MR imaging compared with the contralateral normal side and periglandular stranding can be seen. Microabscesses within the parotid tissue may be seen in a person who has sialectasis and/or sialadenitis. They are identified on CT as areas of low density with peripheral rim enhancement and on MR as areas of very bright signal intensity on T2WI of the salivary glands. Microabscesses are often multiple and may be a source of painful parotid glands with fever. Abscesses may also develop around the mandible, sublingual gland, or submandibular gland in association with dental infections ( Fig. 14-7 ).

A wide variety of inflammatory conditions may affect the salivary glands. Although mumps may be the most common infection to affect the salivary glands (specifically the parotid glands), imaging is unnecessary; the diagnosis is a clinical one. Other viral etiologies include HIV, coxsackie, and influenza viruses. Bacterial infections are uncommon and are usually due to Streptococcus, Haemophilus, and Staphylococcus species.

Other etiologies of acute parotitis include granulomatous (tuberculosis, candida, cat scratch fever) and idiopathic causes (e.g., postpartum parotitis). Poor dental hygiene may contribute to the development of infections affecting the submandibular, sublingual, and parotid glands. The minor salivary glands rarely show inflammatory change other than mucous retention cysts from local obstruction. Vallecular retention cysts, believed to arise from salivary tissue at the tongue base, can get huge.

Sialodochitis

Sialodochitis refers to inflammation of the main salivary ductal system. A number of autoimmune conditions may cause sialadenitis and sialodochitis. Mikulicz disease, or in the most recent classification, Sjögren type 1 disease (poor Dr. Mikulicz is getting squeezed out), is an autoimmune disorder that causes chronic sialadenitis and sialodochitis and leads to fibrous salivary gland tissue (primarily of the minor glands) with resultant dry mouth. This disorder usually affects middle-aged women. They have a higher rate of stones also so do the scan “dry” (Ha!). When the disease is associated with a collagen-vascular disease (most commonly rheumatoid arthritis more so than systemic lupus erythematosus) and there is involvement of the lacrimal glands, the disorder is classified as Sjögren syndrome (Sjögren type 2). Sjögren syndrome is an autoimmune disorder that causes dry eyes, dry mouth, and arthritis. Patients with Sjögren syndrome have a 10-fold increased risk of lymphoma, which may have its first manifestations in the parotid glands. The lymphoma is usually of the non-Hodgkin variety and may also affect any other area of the head and neck ( Fig. 14-8 ). These patients are often scanned to survey for the possibility of lymphoma.

Sjögren syndrome is characterized on conventional or MR sialography by punctate, globular, cavitary, or destructive appearance of the ducts of the parotid glands. Tiny pools of contrast may be seen in the gland. With increasing severity of disease there is greater and greater replacement of glandular tissue with fat. Thus, some have suggested that the severity of fat deposition correlates well with the impairment of salivary flow in Sjögren patients. Sjögren syndrome is also associated with the presence of lymphoepithelial cysts and nodules akin to those seen in patients with HIV-associated parotid lesions (see following discussion).

The cross-sectional imaging appearance of parotid glands in patients who have Sjögren disease may range from normal to a dried up, scarred down, atrophic gland, to one with lots of large and/or tiny cysts and nodules within it, to one with a dominant mass within it. This looks very much like acquired immunodeficiency syndrome (AIDS)–related parotid disease (see later discussion).

The glands with autoimmune sialadenitis generally are denser on CT than normal. Some authors have described a “salt and pepper” appearance (there is that same old food analogy) to the gland on both T1-weighted imaging (T1WI) and T2WI in 46% of patients with Sjögren syndrome, presumably reflecting fibrosis and lymphocytic infiltration intermixed with sialectasis. Biopsy should be performed on any dominant mass to rule out lymphoma.

Lymphoepithelial Lesions

Since the ascent of AIDS in the young population, lymphoepithelial lesions of the parotid gland have become much more common. These may include purely cystic lesions or solid lesions of lymphoid aggregates ( Fig. 14-9 ). Therefore, in a younger patient with multiple lesions in the parotid gland, you should consider lymphoepithelial lesions as opposed to multiple Warthin tumors. The differential diagnosis also includes multiple intraparotid lymph nodes and/or lymphoma. The lymphoepithelial lesions of the parotid have been associated with HIV seropositivity, and the presence of these abnormalities may predate the infection that classifies the patient as having AIDS. Associated findings with the HIV-related parotid disease include diffuse generalized lymphadenopathy in the neck and prominence of adenoidal and tonsillar tissue. Bone marrow signal intensity on T1WI may be lower than normal. When the lymphoepithelial lesion is cystic, it has low density on CT and signal intensity characteristics of cerebrospinal fluid on T1WI and T2WI. However, the lymphoepithelial solid nodules may have a more variable density and signal intensity on cross-sectional imaging. They are not distinguishable from Sjögren-related benign lymphoepithelial lesions (BLELs).

Sialocele

A sialocele refers to a collection of saliva that communicates with the parent duct in a manner similar to that of a pharyngocele or a laryngocele filled with fluid ( Fig. 14-10 ). The most common cause of sialoceles is penetrating trauma, although blunt trauma may also cause disruption of the duct and leakage of salivary contents into the parenchyma and outside the gland. This most commonly occurs in the parotid gland, either from a punch to the side of the face or from a stab wound. The entity is distinguished from a pseudocyst because it communicates with the parent duct and is not lined by fibrous tissue.

Ranula

This is a postinflammatory pseudocystic lesion that results from obstruction and focal rupture of either the sublingual or submandibular duct and that produces a cystic mass either confined by the mylohyoid muscle (simple ranula, epithelial lined) or extending to the submandibular region (a plunging ranula, not epithelial lined) by passing through the mylohyoid dehiscence known as the “boutonniere” (see Fig. 13-24 ). The name ranula is derived from the word “rana,” which means frog in Latin, since the shape of the pseudocyst has been likened to that of a frog. A ranula has also been termed a “mucous escape cyst,” a mucous retention cyst, and a mucocele of the sublingual gland or neighboring minor salivary glandular tissue. The simple ranula is usually addressed transorally, but may be treated with resection or, in some cases, marsupialization. The lingual and hypoglossal nerves must be carefully identified during the operation. A plunging ranula may be excised through a transcervical submandibular incision with a neck dissection. This allows complete resection of the cyst and will help spare the lingual and hypoglossal nerve. Alternatively, the surgeon may excise the sublingual gland transorally and pack the cyst or place a drain in it. By treating the gland, some believe the plunging cyst will resolve on its own.

Retention Cysts

Retention cysts are very common benign “masses” that result from inflammation and obstruction of minor salivary gland ducts and therefore may be seen throughout the aerodigestive system’s mucosal surface.

Miscellaneous Inflammatory Disorders

Sarcoidosis may also affect the parotid gland, usually manifesting as bilaterally enlarged glands with multifocal nodules. Gallium uptake on nuclear medicine scans may be striking. Multiple tiny calcifications in the parotid glands may be seen in sarcoidosis, Sjögren, tuberculosis, and lupus.

A mucus plug in the duct may also cause a painful swollen gland (Kussmaul disease). An inflammatory pseudomass associated with calcifications in the gland is termed the “Kuttner tumor,” a focal firmness of the submandibular gland caused by chronic sialadenitis from sialolithiasis.

Pleomorphic Adenoma

Nearly 80% of benign parotid neoplasms are pleomorphic adenomas ( Box 14-3 ). Pleomorphic adenomas, also known as benign mixed tumors (BMT), occur most commonly in middle-aged women. Most pleomorphic adenomas are well-defined lesions that commonly appear solid and round. Pleomorphic adenomas are well identified on both CT and MR against the fatty background of the normal adult’s parotid gland ( Fig. 14-11 ). On CT, the lesions have density similar to that of muscle and demonstrate mild to moderate enhancement. On dynamic MR and CT scanning, a time to peak of less than 120 seconds and washout ratio of less than 30% suggests malignant tumors over benign with 91% accuracy. This appears to correlate with microvessel count and cellularity. An overlap of peaks between malignancies and Warthins occurred but not with washout ratios.

With a delay, one may see an increase in the degree and homogeneity of enhancement in parotid pleomorphic adenomas. On MR, the lesions are best identified on T1WI amid the bright signal of the parotid fat; however, they are usually seen on T2WI as very bright lesions (add that to your 80% rule; 80% of bright lesions in the parotid are pleomorphic adenomas). Additional MR findings include a complete capsule (often low intensity on T2WI) and a lobulated contour. Pleomorphic adenomas inconstantly have cystic degeneration or calcification within them. Because the incidence of calcification is so much lower in other types of parotid tumors, the presence of calcification nonetheless suggests pleomorphic adenoma.

Pleomorphic adenomas are the most common tumor of the parotid gland in both its superficial and deep portions. In fact, pleomorphic adenomas are the most common benign tumor of the submandibular, sublingual, and minor salivary glands. If you guess pleomorphic adenoma, you will have a better batting average than Ted Williams. They are multicentric in 0.5%, but as they account for 80% of benign tumors and benign tumors are 80% of all tumors, this means that approximately 3% of multiple parotid neoplasms are pleomorphic adenomas.

If left alone to grow, a pleomorphic adenoma will degenerate into or coexist with a carcinoma ex pleomorphic adenoma in a significant (10% to 25%) percentage of cases within 25 years. Yelled the ENT surgeon, “Cut it out!” It is not known whether a carcinoma is present within the pleomorphic adenoma from its outset (malignant mixed tumor) or whether this is a manifestation of malignant transformation (carcinoma ex pleomorphic adenoma), but most pathologists favor the latter theory ( Fig 14-12 ). The luminal epithelial cells undergo malignant change more commonly than the myoepithelial cells. In any case, it is because of this carcinomatous association that pleomorphic adenomas are removed in their entirety with a cuff of normal salivary tissue in most instances.

Rarely, they may metastasize (metastasizing pleomorphic adenoma). The average age of carcinoma ex is 20 years older than pleomorphic adenoma, lending support to the theory of malignant degeneration of a benign tumor.

Monomorphic adenomas (myoepitheliomas, oncocytic adenomas, canalicular adenomas) look very much like pleomorphic adenomas but are more commonly seen in submandibular glands. They are well defined and enhance.

Warthin Tumor

Warthin tumors are also known as cystadenoma lymphomatosum. Guess what? They can be cystic or lymphoma-like in their appearance. These tumors are nearly exclusive to the parotid gland and are the most common multiple and bilateral tumors in the parotid ( Box 14-4 ). As opposed to pleomorphic adenomas, which are generally seen in middle-aged women, Warthin tumors are most commonly seen in elderly men. Warthin tumors may have a tumoral cyst and favor the parotid’s tail (think dirty old men chasing tail). These lesions are entirely benign and show no evidence of malignant transformation. Therefore, if an FNA identifies a lesion as a Warthin tumor, surgeons may conservatively watch the tumor rather than remove it, although that may break their heart. On MR, the lesions are well seen hypointense masses on T1WI contrasting with the native high signal intensity of the parotid gland. However, the signal intensity on T2WI is often heterogeneous and variable and may overlap that of the bright signal of pleomorphic adenomas ( Fig. 14-13 ) or the darker intensity of malignancies of the parotid gland (see following section). Warthin tumors, like oncocytomas, have increased uptake on technetium 99m pertechnetate nuclear medicine scans. Therefore, if an FNA is equivocal or nondiagnostic, you could recommend a nuclear medicine technetium scan to make the diagnosis of Warthin tumor.

Oncocytoma

The oncocytoma is a relatively rare benign tumor almost exclusively seen in the parotid gland (of the salivary glands). These lesions have been called the vanishing parotid mass because, while they are hypointense on T1WI, they are isointense to the native parotid gland on fat-saturated T2 and postcontrast T1 imaging. The tumors may also take up technetium on nuclear medicine scans.

Hemangioma

Hemangiomas are the most common salivary gland tumors seen in children, girls more than boys. Hemangiomas enhance brightly and are very hyperintense on a T2WI. Cutaneous hemangiomas may coexist. Congenital capillary hemangiomas represent 90% of parotid gland tumors in neonates. They will undergo spontaneous resolution by adolescence in most cases. Low-flow vascular malformations of lymphatic and venous origin are the next most common benign lesions to affect pediatric parotid gland. The third most common benign tumor of the pediatric parotid gland is the pleomorphic adenoma.

Other Benign Tumors

Lipomas, schwannomas ( Fig. 14-14 ), and neurofibromas may also be seen in association with the salivary glands, most commonly the parotid. Lipomas have fat density and present in children. The neurogenic tumors generally follow cranial nerves V (submandibular, sublingual, and parotid glands) or VII (parotid glands). Be careful to trace these tumors along the expected course of the nerves, even to their foramina. What lies at the bottom of the ocean and twitches? A nervous wreck.

Mucoepidermoid Carcinoma

Mucoepidermoid carcinomas account for 30% of all salivary gland malignancies, and is the most common malignant lesion of the parotid gland (60% of them occur in the parotid gland; Fig. 14-15 ). Mucoepidermoid carcinomas, like squamous cell carcinoma, can be graded from low to high, and the prognosis varies with the grade. Mucoepidermoid carcinoma is the most common pediatric salivary gland malignancy. Thirty-five percent of salivary gland neoplasms in children are malignant and of these, 60% are mucoepidermoid carcinomas. Primary salivary gland lymphoma does occur in the parotid gland as can leukemic infiltration in children.

In the parotid gland, a lesion’s morphology may be misleading as far as predicting benignity versus malignancy. Some pleomorphic adenomas have tentacles with an irregular margin. By the same token, some mucoepidermoid carcinomas are well defined by a pseudocapsule and do not appear to be invasive. Therefore, you cannot rely on definition of margins to distinguish cancer from benign tumors. Just like shape cannot differentiate one Jenner from the true Jenner.

On CT, most tumors of the parotid gland have a density equal to muscle—no help there. Low-grade mucoepidermoid carcinomas may have high T2W signal intensity, but high-grade, poorly differentiated mucoepidermoid carcinomas and parotid malignancies of other histologies are usually low in intensity on T2WI. A useful adage is that if the T2W signal intensity is low, the lesion should be biopsied for probable malignancy (careful, Warthin tumors may be dark on T2WI and simulate a high-grade mucoepidermoid carcinoma). If the lesion is bright on T2WI, you can assume it is a pleomorphic adenoma and proceed accordingly without presurgical sampling. MR also does well in demonstrating the perineural, vascular, and dural invasion that may be present with parotid malignancies. Malignancies enhance, have low apparent diffusion coefficient (ADC) values, and have lower blood flow and blood volume (compared with benign parotid tumors in contradistinction to brain tumors).

Adenoid Cystic Carcinoma

Adenoid cystic carcinoma (ACC) is the second most common primary malignancy of the parotid gland and the most common tumor of the submandibular, sublingual, and minor salivary glands. Similar to the mucoepidermoid carcinoma, variable intensity occurs with the T2WI ( Fig. 14-16 ). Noncystic ACC masses in the parotid gland have muscular CT density, low intensity on T1WI, and mild to moderate enhancement. ACCs are notorious for their propensity for perineural spread (50% to 60%) and persistence despite “complete surgical removal.” They are like dust mites; you cannot get rid of them, they keep multiplying, and you learn to live with them. An ACC of the parotid gland may spread via the ramifications of cranial nerve VII retrograde into the temporal bone or may spread via the auriculotemporal branches of cranial nerve V to the Meckel cave region through the foramen ovale (see Fig. 14-16, B ). In the other salivary glands, adenoid cystic carcinoma generally demonstrates perineural extension along the branches of the second and third divisions of cranial nerve V. This cancer is a relentless, slow-growing tumor whose prognosis is generally measured in terms of decades rather than 5-year survival rate because of its prolonged course.

Squamous Cell Carcinoma

Squamous cell carcinoma may be seen within the parotid gland. Sometimes it is difficult to tell whether the squamous cell carcinoma is present secondarily because of invasion of lymph nodes from a primary site outside the parotid or is intrinsic to the parotid gland ( Fig. 14-17 ). How it gets there is mysterious because squames are not intrinsic to glandular tissue; they are presumably caused by metaplasia of the ductal columnar epithelium into squamous cells. This same difficulty lies with lymphoma of the parotid—is it a primary parotid tumor or secondary spread? When multifocal in the parotid, it is generally accepted that the squamous cell carcinoma is probably within lymph nodes in the parotid gland. A search for a primary tumor is undertaken in the overlying skin and ear as primary sites that drain to the parotid gland. Squamous cell carcinoma does not generally occur in submandibular, sublingual, or minor salivary glands as a primary site, although it certainly spreads to them from adjacent mucosal surfaces. Squamous cell carcinomas are virtually always hypointense on T2WI unless necrosis coexists.

Adenocarcinoma

Adenocarcinomas may also arise within the parotid gland, sublingual gland, submandibular gland, or minor salivary glands. This lesion generally has a worse prognosis than that of mucoepidermoid carcinoma and adenoid cystic carcinoma ( Box 14-6 ). This tumor is derived from the glandular tissue itself as opposed to ductal tissue. Signal intensity is variable, depending on mucinous, cystic, or solid contributions, but usually dark on T2WI and enhance. Remember that some adenocarcinomas (carcinoma ex) occur from malignant degeneration of pleomorphic adenomas.

The polymorphous low-grade adenocarcinoma of the salivary gland (PLAC) is a low-grade neoplasm that predominantly occurs in the minor salivary glands of the oral cavity (mucosa of the soft and hard palates, in the buccal mucosa, and in the upper lip) but can be seen in the parotid gland. It has a much more benign prognosis and course than the traditional butt-kicking adenocarcinoma.

Acinic Cell Carcinoma

Acinic cell carcinoma ( Fig. 14-18 ) is the most common primary multifocal malignancy to affect the parotid gland. Its prognosis is intermediate between that of mucoepidermoid carcinoma and adenocarcinoma of the parotid gland. This tumor is seen almost exclusively in the parotid gland, and the incidence of bilateral acinic cell carcinomas is approximately 1% to 3%. No specific imaging features other than its multifocality suggest this diagnosis. Consider it the spitting image of adenocarcinoma (pun-time!)

Undifferentiated Carcinoma

Undifferentiated carcinoma is also seen as a salivary gland tumor. This lesion has a very poor prognosis but fortunately is rarely seen.

Metastatic Adenopathy

The incidence of nodal metastases in untreated parotid cancers is low except in T3 or T4 lesions. Although mucoepidermoid carcinoma and squamous cell carcinoma metastasize to nodes in 37% to 44% of cases, the other histologic types are only associated with lymphadenopathy in 5% to 21%, with adenoid cystic carcinoma being the lowest. ACC “plucks” your nerves instead of nodes.