The clinical significance of tumor-associated antigen RCAS1 expression in the normal, hyperplastic, and malignant uterine endometrium

Objective. A tumor-associated antigen, RCAS1, is recognized by 22-1-1 monoclonal antibody. It was found in carcinomas derived from the uterus and ovary and was especially strongly expressed in invasive cancers. A previous investigation showed the RCAS1 expression to be correlated with a poor prognosis in uterine cervical adenocarcinoma. In this study, we examined whether the expression of RCAS1 is associated with the progression of the uterine endometrial neoplasms. Methods. The expression of RCAS1 was evaluated by an immunohistochemical analysis. The tissue specimens used in this study included 46 cases of normal uterine endometrium, 40 cases of hyperplasia, and 121 cases of adenocarcinoma. The relationship between RCAS1 expression and several clinicopathological variables (clinical stage, histology, grade, myometrial invasion, lymph-vascular space invasion, and lymph node metastasis) was also assessed in endometrial adenocarcinoma. Results. RCAS1 was positive in 26% of the normal uterine endometrium specimens (12 of 46 total cases), in 32% of the hyperplasia specimens (13 of 40 total cases), and in 68% of the adenocarcinoma specimens (83 of 121 total cases). As a result, the expression of RCAS1 was statistically higher in adenocarcinoma than in the normal and hyperplastic endometrium (P < 0.0001). RCAS1 was statistically detected more frequently in grade 3 than in grade 1 or 2 (P < 0.05); however, there was no correlation between the antigen expression and the clinical stage, myometrial invasion, lymph-vascular space invasion, or lymph node metastasis. Conclusion. RCAS1 expression might thus be associated with the malignant transformation and poor differentiation observed in uterine endometrial adenocarcinoma. (C) 2000 Academic Press.