Immunohistochemical characterization of cancer antigen in uterine cancers

The pattern of cancer antigen (CA-125) expression by immunohistochemistry (IHC) was investigated in malignant and nonneoplastic endometrium in endometrial carcinoma. Ninety cases of primary uterine carcinomas (65 endometrioid [EM] carcinoma, 15 serous papillary [SP] carcinoma, 6 carcinosarcomas [malignant mixed müllerian tumors], and 4 clear cell carcinoma [CC]) and adjacent atrophic and/or hyperplastic endometrium were analyzed by IHC for CA-125 expression. The percentage and intensity of luminal, apical, basal, and diffuse cytoplasmic immunostaining of epithelial cells were categorized on a scale of 0-4. The immunoreaction score (IRS score) was calculated and correlated with the grade and stage of carcinoma according to the histologic type. CA-125 expression (3-4/4) was localized in apical borders of grade 1 and grade 2 EM carcinoma and was weak or negative (0-1/4) in grade 3 EM. Mucinous differentiation in EM was associated with intense luminal and apical staining. Squamous areas and stroma showed no staining at all. SP carcinoma and endometrial intraepithelial carcinoma showed much higher mean IRS score than EM. In malignant mixed müllerian tumors (MMMT), the epithelial component stained as above according to the type of epithelial cell differentiation of the neoplastic cells. Benign proliferative glands showed moderate apical luminal, basal, and cytoplasmic staining. Intense diffuse staining was observed in atypical complex hyperplasia. Different patterns of CA-125 immunostaining were observed in normal, hyperplastic, and neoplastic endometrium. IRS score correlated with the grade but not with the stage of EM carcinoma. The intense different staining pattern of endometrium with atypical complex hyperplasia suggests that CA-125 may be a useful diagnostic aid.