ULTRASTRUCTURAL LOCALIZATION OF CA 19-9 IN OVARIAN CANCER

Four cases of ovarian cancer (mucinous cystadenocarcinoma, serous cystadenocarcinoma, endometrioid carcinoma and metastatic cancer of the colon) which revealed diffuse localization of carbohydrate antigen 19-9 (CA 19-9) in their tumor tissues were subjected to immunoelectron microscopy. In all cases CA 19-9 was present in plasma membranes, microvilli and glycocalyx in mucinous and metastatic carcinoma, indicating that the antigenic determinant for CA 19-9 is sialylated Lewis A. Reaction products were seldom seen in perinuclear spaces and endoplasmic reticula. Many pictures revealed positive vesicles apparently released from the Golgi apparatus; this feature seemed to be characteristic of the findings. Thus, the Golgi apparatus is considered to be the place where immunoreactive CA 19-9 is first produced in cancer cells. Since positive images were found not only in organelle but also on collagen fibers directly under the basement membranes, it seemed that an important factor for CA 19-9 increase in the blood is the expansion of CA 19-9 to stroma. It was strongly suggested that CA 19-9 was useful as a tumor marker for ovarian cancer which originated in common epithelial cells.