CA 19-9, a side branch of the
Lewis blood group system, is a sialylated Lewis A
antigen that is highly expressed by many
adenocarcinomas of the digestive tract. The müllerian duct-derived mucosa of the uterus and fallopian tubes also synthesizes
Lewis blood group antigens. To test whether the expression of CA 19-9 is enhanced in
carcinomas of müllerian duct origin, we performed immunohistochemical staining for CA 19-9 in normal tissues from 33 women and in
adenocarcinomas from 88 patients. In the normal uterine cervix, CA 19-9 was expressed in the cytoplasm of scattered glandular cells in 26 of 29 specimens. It was observed in the apical regions of mucosal cells in six of 26 normal endometrial samples and two of 13 normal fallopian tube specimens. These results are consistent with the presence of
antigen CA 19-9 on a secretory product of the nondiseased mucosa of the müllerian duct. In
adenocarcinomas of the endocervix, endometrium, and fallopian tubes, CA 19-9 was found in seven of 11, 57 of 71, and five of six samples, respectively. Progressive loss of differentiation was accompanied by disruption of subcellular localization of CA 19-9 and its secretion toward the glandular lumina. In well-differentiated regions of
tumors, the
antigen was detected mainly at the
luminal surface of cancerous glands, whereas the staining was mostly cytoplasmic or vacuolar in less differentiated areas. The degree of CA 19-9 expression was inversely related to
tumor differentiation (P less than .001).