Cellular localization of keratin in proliferative epithelial processes and neoplasms of the human ovary.

Cytokeratins are one of the intermediate cytoplasmic filaments which contribute to the cytoskeleton. Keratins have recently been demonstrated in normal and neoplastic tissues as well as in human cell lines. It has been suggested that the cellular location of keratin may reflect tissue-specific or epithelial type differentiation. Twenty-three examples of human ovaries containing the full spectrum of epithelial proliferations from inflammatory reactive processes to malignant neoplasia were studied for the cellular distribution of cytokeratin using antisera to human keratin. Nineteen cases contained immunoreactive keratin which was limited to the epithelial cells: 2/2 inflammatory, 8/10 benign tumors, 5/7 borderline tumors, 4/4 carcinomas. There was marked regional heterogeneity in keratin expression such that adjacent morphologically-identical cells could be functionally distinguished by the immunoreactive staining. The predominant cellular localization of keratin varied between histological tumor types in the benign neoplasms: serous = apical, subciliary; endometrioid = apical; mucinous = basal. This pattern was lost in the cytological progression to borderline and malignant tumors. In borderline tumors, the most intense reactivity was noted in areas of cellular atypia and proliferation. In borderline and malignant tumors, keratin was usually present in basal cytoplasmic regions contiguous with stroma.