Immunohistochemical demonstration of relaxin in gynecologic tumors

The immunoperoxidase technique was utilized to study the occurrence and localization of relaxin in malignant and nonmalignant trophoblastic disease and nontrophoblastic gynecologic cancer. Tissue specimens were studied from normal placenta at various weeks of gestation (N = 10), hydatidiform mole (N = 10), invasive mole (N = 10), choriocarcinoma (N = 10), normal endometrium (N = 28), decidua (N = 5), adenocarcinoma of the endocervix (N = 10), of the endometrium (N = 10), corpus luteum (N = 2), ovarian serous papillary cystadenocarcinoma (N = 10), and mucinous cystadenocarcinoma (N = 10). Relaxin was identified in the syncytiotrophoblast of normal placenta at all stages of gestation and also, for the first time, in hydatidiform mole, invasive mole, and choriocarcinoma. No relaxin was found in any nontrophoblastic cancer, including secretory-type adenocarcinoma. The absence of relaxin in the secretory-type endometrial adenocarcinoma is intriguing in light of the finding of relaxin in the normal secretory endometrium. The difference may be due to absence of the relaxin-producing corpus luteum in cancer patients or to loss of relaxin synthesis in the malignant endometrium. The results of this study suggest that relaxin may be synthesized by the normal syncytiotrophoblast and trophoblastic tumors, although differential absorption of relaxin produced in another site cannot be excluded.