PT - JOURNAL ARTICLE AU - T. Arai AU - J. Watanabe AU - M. Kawaguchi AU - Y. Kamata AU - Y. Nishimura AU - T. Jobo AU - H. Kuramoto TI - Clear cell adenocarcinoma of the endometrium is a biologically distinct entity from endometrioid adenocarcinoma AID - 10.1136/ijgc-00009577-200601000-00063 DP - 2006 Jan 01 TA - International Journal of Gynecologic Cancer PG - 391--395 VI - 16 IP - 1 4099 - http://ijgc.bmj.com/content/16/1/391.short 4100 - http://ijgc.bmj.com/content/16/1/391.full SO - Int J Gynecol Cancer2006 Jan 01; 16 AB - Clear cell adenocarcinoma (CCA) of the endometrium has a poor prognosis, although the biologic features of this rare tumor are not clear. In this study, we analyzed the expression of biologic markers relating to carcinogenesis, tumor growth, and progression. Thirteen cases of CCA were compared with cases of endometrioid adenocarcinoma (EMA) of the endometrium. Immunohistochemical staining for p53; Ki-67; cyclins A, D1, and E; E-cadherin; progesterone receptor (PR)-A and PR-B; P-glycoprotein; MLH1; and MSH2 was performed. Labeling indices of p53, Ki-67, and cyclins A, D1, and E in CCA were 46.4 ± 24.3%, 52.1 ± 20.5%, 37.9 ± 21.4%, 12.3 ± 27.9%, and 8.2 ± 22.9%, respectively. E-cadherin was expressed in only 1 case (7.7%) of CCA, as compared to 39 cases (61.0%) of EMA. No CCAs were positive for PR-A and PR-B. P-glycoprotein was detected in seven cases (53.8%). Loss of either MLH1 or MSH2 expression occurred in eight cases (61.5%). High-level expression of p53, cyclin A, and P-glycoprotein, and low-level or no expression of cyclin E, E-cadherin, PR-A, and PR-B was observed in CCA compared with EMA. The mechanism of cell-cycle regulation in endometrial CCA is different from that in EMA and may influence its malignant potential. Endometrial CCA is a distinct entity from EMA.