MONOCLONAL-ANTIBODY, MAB 12C3, IS A SENSITIVE IMMUNOHISTOCHEMICAL MARKER OF EARLY MALIGNANT CHANGE IN EPITHELIAL OVARIAN-TUMORS

A murine monoclonal antibody (MAb 12C3) that is specific to human ovar ian carcinomas was generated bg immunizing mice with a human ovarian g erminoma cell line (JOHYC-2). The antigen distribution that was define d by MAb 12C3 in normal and malignant human tissues was analyzed by im munohistochemistry on paraffin-embedded and frozen sections. The antib ody reacted with 67.7% (21 of 31 cases) of epithelial ovarian carcinom as (6 of 12 cases of serous cystadenocarcinoma, 5 of 7 cases of mucino us cystadenocarcinoma, 7 of 9 cases of clear cell carcinoma, 3 of 3 ca ses of endometrioid adenocarcinoma), but did not react with any of the benign epithelial ovarian adenomas tested. Partial regions of borderl ine ovarian malignancies that exhibited marked papillary projection of the lining cells with cellular atypia reacted positively with MAb 12C 3 in 14 of 25 cases (56.0%). The histologic features of regional early malignant change corresponded to the expression of the MAb 12C3 epito pe in the borderline malignant tumor cells. There was a low frequency of reaction (4.3%) between the antibody and other gynecologic and nong ynecologic malignancies (46 cases of 12 tissues). In normal tissues, t he antibody reacted positively with only three tissues, including corp ora lutein cells, excretory ducts in the submandibular gland, and basa l cells of the sebaceous glands. The antigen epitope defined by MAb 12 C3 was present on a glycoprotein with a molecular mass of 200 kDa and did not exhibit any crossreactivity with other well-known tumor marker s. These data suggest that MAb 12C3 may be a useful tool for the immun ohistologic detection of early malignant changes in epithelial ovarian tumors. In addition, MAb 12C3 also may facilitate a differential diag nosis between benign end borderline malignancies.