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Carcinoma in situ and microinvasive cancer of the cervix were compared by transmission electron microscopy to examine ultrastructural features of the locally infiltrating lesion of microinvasive cancer. Many pseudopod-like cytoplasmic protrusions of the cancer cells and abundant microfilaments parallel to the direction of the protrusion were seen. Concomitant with the disappearance of part of the basal lamina, many vesicles 70-90 nm in diameter were observed, suggesting a role for these vesicles in cancer infiltration. With the immunoperoxidase method, the distribution of fibronectin around the invasive lesion also was examined. Fibronectin is a component of extracellular matrices and presumably, in view of its action on cell adhesion, is a resistant factor against cancer cell infiltration. Fibronectin decreased in the transitional area between the cancer nest and the stroma during the stage of microinvasion.

The location of transferrin receptor (Tf.R) which is abundantly contained in proliferating cells and positional relationships of cells containing much Tf.R was observed on cervical and endometrial tissue sections by immunohistochemistry. In normal squamous epithelium, the parabasal cell layer was positive and the basal, intermediate, and superficial cell layers negative. This shows that the cells of the parabasal cell layer are proliferating most actively among those layers. Squamous carcinoma contained many positive cancer cells. But negative as well as positive cells were present, indicating that cancer cells proliferate under various conditions. Cancer cells infiltrating the stroma were made clear by Tf.R staining, and it became easier to identify them when only a few were present. Endometrial glandular cells in the basal layer stained only on the basal side of a cell regardless of the menstrual cycle, whereas in the functional layer glandular lumen side also stained positive in the secretory phase. Based on the present data, an immunohistochemical study of Tf.R seems useful to confirm the localization of proliferating cells and cancer cells and determine the conditions for cancer cell proliferation on the tissue sections.