Human chorionic gonadotropin in the rectosigmoid colon. Immunohistochemical study on unbalanced distribution of subunits.

For investigation of cellular localization of subunits of human chorionic gonadotropin (hCG) in normal and neoplastic rectosigmoid colon, immunohistochemical studies were performed on nonneoplastic colons (10 fetuses, 3 infants, and 23 adults, including 4 cases of ulcerative colitis) and 7 carcinoid tumors, 19 adenomas, and 50 carcinomas of the rectosigmoid colon. The alpha-hCG immunoreactive cells were present in endocrinelike cells of non-neoplastic glands (6 fetuses older than 14th gestational week, 3 infants and 19 of 23 adults). Many of the positive cells were argyrophilic, and all were nonimmunoreactive for beta subunits of glycoprotein hormones. alpha-hCG immunoreactivity was also present in many argyrophilic cells of all carcinoid tumors and in some of the endocrine cell micronests. The immunoreactive cells for isolated beta-hCG were found in 14 infiltrating carcinomas. The distribution of hCG subunits was unbalanced, and both subunits may be expressed through an independent mechanism, commonly in normal and neoplastic rectosigmoid colon.