Cervical Squamous Cell Carcinoma

Tumor Volume and Lateral Extent of Spread

Although, as discussed above, it is generally accepted that depth of the invasion correlates with prognosis, other studies have documented that the tumor volume might be an even better prognostic measure. In order to accurately determine tumor volume, an excisional specimen needs to be serially step sectioned. When this is done and the distance between the sections is known, tumor volume can be calculated. This approach was first advocated by Burghardt and Holtzer, who reported no pelvic lymph node metastases in patients with <420 mm ³ of cancer unless lymphovascular space involvement was identified. However, performing serial step sections to assess tumor volume is not practical for most laboratories. Thus FIGO has recommended that the greatest lateral extent of the tumor be measured as a surrogate for tumor volume. The usefulness of lateral tumor extension as a prognosticator was shown in an analysis of 402 women with squamous cell carcinomas by Takeshima et al. In this study, the incidence of nodal metastases was only 1.2% among patients with ≤3 mm of invasion but increased to almost 7% among women with 3–5 mm of invasion. However, in both groups, almost all recurrences occurred in women with >7 mm of horizontal spread. Based on these and other data showing the importance of lateral tumor extension, the FIGO staging system now requires stage IA tumors to be ≤7 mm in greatest diameter. This was reaffirmed by the LAST group, which defines SISCCA of the cervix as having no more than 7 mm in maximal extent.

Lymphovascular Invasion

The role of lymphovascular invasion (LVI) as a prognostic indicator is more controversial than that of the depth of invasion and lateral extent of tumor. Although it would seem reasonable to assume that a tumor with LVI is more likely to have lymph node metastases than one without, the data are conflicting. In part, this stems from the relatively poor reproducibility of a pathologic diagnosis of LVI, especially when not extensive. It is well documented that the stroma in which foci of invasion lie can retract during preparation of the tissue sections for microscopic examination. A clear space can easily be mistaken for LVI. Another problem with the reporting of LVI is the fact that the finding is contingent on the number of sections that are examined. In one study serial step sections were examined from 30 cervices diagnosed with cervical carcinoma having only 2–5 mm of invasion. Thirty percent of the women had ‘capillary-like space’ involvement based on the first cut of tissue from the blocks, but this increased to 57% when the serial step sections were examined. All of the women in this study had been treated with radical hysterectomy with lymph node dissection. No lymph node metastases were found, regardless of the presence or absence of LVI. This study concluded that the presence of tumor in lymphatic spaces was of no value by itself in predicting which patients are likely to have lymph node metastases. However, other studies have reported that the presence of LVI is an important prognostic indicator. For example, a recent literature review of carcinomas with <3 mm of invasion reported recurrent cancer in 3.1% (3 of 96) of conservatively managed patients with LVI versus only 0.6% (3 of 486) of those without LVI. Overall, LVI has been reported in 0–10% of carcinomas invading <1 mm and 3–30% of those invading 1–3 mm.

Stromal Invasion

A diagnosis of SISCCA is made based on finding buds or tongues of malignant cells penetrating the basement membrane and extending into the stroma. The earliest stage at which invasion can be recognized is when a well-defined, tiny bud of invasive cells emanates from the base of HSIL on the surface of the cervix or in endocervical glands ( Figure 11.1 ). The bud projects into the stroma, clearly having disrupted the adjacent smooth basement membrane. In one large series a single bud accounted for one-third of all the microinvasive cancers. However, in other cases, multiple small buds and sometimes individual tumor cells extend into the stroma.

A number of different histologic patterns of SISCCA have been described. In very early foci of invasion the tumor cells are often separated by <1 mm from the nearest involved surface or glandular basement membrane. Cases with <1 mm tumor invasion were previously referred to as ‘early stromal invasion,’ which was the original definition of the FIGO substage IA1 in the 1985 FIGO classification. Another common pattern of growth is when microinvasive cancers appear as tiny nests of cells extending into the stroma that are totally separated from the overlying surface ( Figures 11.2 and 11.3 ). This pattern of invasion has been referred to as a ‘spray bud’ pattern. The spray bud pattern of growth is usually <1–2 mm deep. As the foci of invasion become larger, the growths become broader and longer and eventually, as the tumor becomes more advanced, a ‘confluent’ pattern develops ( Figure 11.4 ). In these larger lesions the invasive foci often form intertwining cords, much like thick tangled roots of a tree. It is important to stress that reproducible definitions of different patterns of invasion such as spray bud and confluent have proven difficult to develop and, not surprisingly, most studies have shown that the pattern of invasion does not influence clinical outcome independently of depth of invasion.

It is frequently difficult to determine whether a given focus represents SISCCA or instead is HSIL that extends into endocervical glands. There are four qualitative histopathologic features that can help with the diagnosis of SISCCA, in addition to measured limits of extent ( Table 11.3 ). The first is presence of an epithelial margin that can be described as irregular, ragged, or even scalloped in appearance ( Figure 11.5 ). This irregular margin develops because the adjacent smooth basement membrane has been disrupted. The second histopathologic feature is increased cellular maturation compared to the adjacent HSIL. The cells in the invasive foci often have abundant eosinophilic cytoplasm and are paradoxically keratinized ( Figure 11.6 ). The third feature is that the nuclei of the invasive cells frequently show clearing of the chromatin and develop prominent nucleoli ( Figure 11.7 ). The fourth feature is a stromal reaction to the SISCCA. Invasive foci are often surrounded by a prominent lymphoplasmacytic infiltrate and the stroma frequently has a desmoplastic response ( Figure 11.3 ).

Measuring Depth of Invasion and Lateral Extent of Spread

Of all the variables evaluated during the assessment of SISCCA, depth of invasion is the one that is universally considered the easiest to measure and the most objective. The interobserver variability in assessing depth of invasion is also considered to be the lowest among the various features considered to have prognostic value. In order to accurately determine the maximum depth of invasion, loop electrosurgical excision procedure (LEEP) and conization specimens should be sectioned along the long axis of the cervical canal in a clockwise fashion while trying to avoid tangential sections, which invariably result in inaccurate measurement of the depth of invasion. The current FIGO/LAST staging method recommends that measurement of depth of invasion be made from the base of the epithelium where invasion occurs to the deepest point of carcinoma in a vertical line. In most SISCCAs, invasion either occurs from the base of the surface squamous epithelium or originates from both the surface epithelium and endocervical glands simultaneously. In such cases, measurement should be made from the base of the surface epithelium involved by HSIL. In some cases invasion is limited to the periphery of a few endocervical glands without surface involvement. In these cases, measurement is made from the base of the glands to the deepest point. The deepest measurement should be reported when multiple foci of SISCCA are present.

The lateral extent of SISCCA is usually measured directly from the microscopic slides using a micrometer or ruler as well as by determining the number of contiguous tissue sections that have microinvasive carcinoma. Since most tissue blocks submitted for histologic processing are 2–3 mm in thickness, if three separate, contiguous tissue blocks show SISCCA it is highly probable that the diameter of the tumor is more than 7 mm and the lesion no longer fits the criteria for superficial invasion, or a FIGO stage IA tumor.

Assessing Presence of LVI

Even though the 2009 FIGO staging system does not take into account the presence or absence of LVI, most gynecologic oncologists want to know this information so that treatment can be individualized. Therefore the pathologist should always provide this information in the pathology report. Lymphatic space involvement was defined back in the 1960s as endothelial-lined (capillary-like) spaces containing tumor cells that are contiguous with the stroma. Until the recent introduction of the antibody D2-40 that specifically identifies lymphatic vessels, it was impractical to tell the difference between lymphatic and blood vessels under microscopy. Therefore the term lymphovascular space involvement, or invasion, came into widespread use when discussing cervical small vessel invasion by tumor, be it capillary or lymphatic. Identification of LVI, especially when only several foci are present, can be quite challenging. There is general agreement that LVI should be diagnosed whenever tumor is seen within endothelial-lined spaces at the leading edge of the tumor or beyond ( Figure 11.8 ). Although it is preferable to identify tumor cells attached to the endothelium, this is not always possible. It is well documented that the stroma in which foci of invasion lie can retract during preparation of the tissue sections for microscopic examination. A clear space can easily be mistaken for LVI. Various immunohistochemical markers such as CD34, a marker for endothelium, and D2-40, a marker of lymphatic epithelium, can assist in identifying LVI in some instances. However, it should be remembered that there are a variety of markers available and the results obtained with them can be discordant. Moreover, it is unclear whether LVI, as determined by immunohistochemical markers, correlates with clinical outcomes. Therefore, the standard for assessing the presence or absence of LVI in the cervix remains H&E staining alone.

Assessing Surgical Margins

Although the 2009 FIGO staging system does not take into account the status of the surgical margins of a conization or LEEP specimen, assessment of the surgical margins of excision is one of the most important contributions of the pathologist to management of women with SISCCA. This is because women with either HSIL or SISCCA on the surgical margin are much more likely to have a residual invasive cervical cancer than are women with clear margins. Inking of LEEP specimens is optional since a thermal artifact is universally present in the resection margin. However, a cold-knife cone requires application of ink at the margins, preferably one color at the endocervical and another on peripheral or deep margins.