Immunohistochemical distribution of tumor-associated antigen CA6 in gynecological neoplasms as detected by monoclonal antibody DS6.

DS6 is a murine monoclonal antibody developed using ovarian papillary serous adenocarcinoma as the immunogen. DS6 immunohistochemically reacts with a tumor-associated antigen, CA6, which has a limited range of expression in normal human tissues and is not expressed by benign mesothelium. We have studied the spectrum of immunohistochemical reactivity of antibody DS6 in 293 formalin-fixed, paraffin-embedded human gynecological neoplasms. The CA6 antigen shows strong expression in serous adenocarcinomas of the ovary (56/58 cases) and endometrium (6/6). CA6 is also expressed by the majority of ovarian endometrioid adenocarcinomas and Brenner tumors and by the majority of endometrioid adenocarcinomas, mucinous adenocarcinomas, and clear cell adenocarcinomas of the endometrium. CA6 is detected in 14% of ovarian clear cell carcinomas and is not detected in ovarian mucinous cystadenomas (0/7), mucinous intestinal-type borderline tumors (0/8), mucinous adenocarcinomas (0/10), or in malignant mesotheliomas (0/8). In neoplasms with papillary or glandular growth patterns, CA6 is detected along luminal cell membranes. CA6 is also seen along peripheral cell membranes and focally in the cytoplasm in some epithelial neoplasms. There is heterogeneity in immunohistochemical staining for DS6 both within an individual neoplasm and between neoplasms. Reactivity is not detected in neoplasms of sex cord-stromal, mesenchymal or germ cell origin.