Cervical conization is required to assess correctly the depth and the linear extent of involvement when microinvasion is suspected. Early invasion is characterized by a protrusion of malignant cells from the stromal–epithelial junction. This focus consists of cells that appear better differentiated than the adjacent noninvasive cells and have abundant pink-staining cytoplasm, hyperchromatic nuclei, and small-to medium-sized nucleoli (11). These early invasive lesions form tonguelike processes without measurable volume and are classified as International Federation of Gynecology and Obstetrics (FIGO) stage IA1. With further progression, more tonguelike processes and isolated malignant cells appear in the stroma, followed by a proliferation of fibroblasts (desmoplasia) and a bandlike infiltration of chronic inﬂammatory cells (Fig. 36.2). With increasing depth of invasion, lesions occur at multiple sites, and the growth becomes measurable by depth and linear extent. Lesions that are less than 3 mm in depth are classified as FIGO stage IA1. Lesions that are 3 to 5 mm or more in depth and up to 7 mm in linear extent are classified as FIGO stage IA2 (12). As the depth of stromal invasion increases, so does the risk of capillary lymphatic space involvement. Dilated capillaries, lymphatic spaces, and foreign-body multinucleated giant cells containing keratin debris are often seen in the stroma.
The depth of invasion should be measured with a micrometer from the base of the epithelium to the deepest point of invasion. Depth of invasion is a significant predictor for the development of pelvic lymph node metastasis and tumor recurrence. Although lesions that have invaded 3 mm or less rarely metastasize, patients in whom lesions invade between 3 to 5 mm have positive pelvic lymph nodes in 3% to 8% of cases (13). The significance of the cutoff at 3 mm is not identified completely; it was postulated that small capillary–lymphatic spaces at this level are incapable of facilitating the transport of malignant cells. Uneven shrinkage of tissue by fixative often creates space between the tumor nests and the surrounding fibrous stroma, simulating vascular lymphatic invasion (Fig. 36.2). Therefore, suspected vascular–lymphatic involvement
Figure 36.2 Microinvasive squamous carcinoma. Multiple irregular tonguelike processes and isolated nests of malignant cells are seen, some surrounded by clear spaces, simulating capillary lymphatic invasion. This is an artifact caused by tissue shrinkage. The depth of stromal invasion is measured from the basement membrane of the overlying cervical intraepithelial neoplasia (CIN). In this case, it is 1.2 mm.
with invasion of less than 3 mm should be interpreted with care. A lack of endothelial lining indicates that the space is a fixation artifact rather than true vascular invasion.
Staging Cervical cancer is a clinically staged disease. The FIGO staging system is the standard and is applicable to all histologic types of cervical cancer. The FIGO staging system is presented in Table 36.1 and Figure 36.3. The staging procedures allowed by FIGO are listed in Table 36.2. When there is doubt concerning the stage to which a cancer should be allocated, the earlier stage should be selected. After a clinical stage is assigned and treatment is initiated, the stage must not be changed because of subsequent findings by either extended clinical staging or surgical staging. The upstaging of patients during treatment will produce an erroneous perception of improvement in the results of treatment of low-stage disease. Following is a breakdown of the incidence of cervical cancer by stage at diagnosis: 38%, stage I; 32%, stage II; 26%, stage III; and 4%, stage IV (3,13,14).