CA 125 in normal tissues and carcinomas of the uterine cervix, endometrium and fallopian tube. I. Immunohistochemical detection.

The distribution of cancer antigen 125 (CA 125) has been investigated in normal tissues and carcinomas of the Müllerian duct by immunohistochemical methods using the monoclonal antibody OC 125. Detection of CA 125 was most intense in cryostat sections and decreased in formalin fixed and paraffin embedded tissues according to the duration of fixation. Enzymatic digestion with neuraminidase or alkaline hydrolysis abolished specific staining suggesting the antigen is a sialylsaccharide bound to protein by alkali-labile linkage. Immunohistochemical staining demonstrated the presence of CA 125 in all normal glandular epithelia of the endocervix, endometrium and fallopian tube in different distribution patterns. In normal endometrium the cellular distribution pattern was related to the menstrual cycle. In endocervical, endometrial and tubal adenocarcinomas CA 125 was found in 73% of cases. In glandular structures the antigen was concentrated at the luminal surface of the tumour cells, in solid tumour areas it was spread throughout the cytoplasm or concentrated in large cytoplasmic vacuoles. The expression of CA 125 was considerably lower in solid tumour areas. These data show that CA 125 is not a true "tumour marker", but a product of female genital mucosae and of their cancerous derivates provided their synthesizing ability is not lost in the course of pathologic differentiation.