Benign and malignant serous and endometrioid epithelium in the omentum

Objectives. Benign and malignant serous and endometrioid epithelial prolife rations are found in the omentum, where their presence may be interpreted e ither as metastases from Mullerian tumors elsewhere or as primary peritonea l tumors. The present study was undertaken in an attempt to gather data tha t might help resolve the issue. Methods. The ratios of serous epithelium to endometrioid epithelium in the omentum, in both the benign and malignant states, were determined for cases from January 1985 to July 1997 and January 1991 to December 1997, respecti vely. Results. In ovarian carcinoma, the ratio of malignant serous epithelium to endometrioid epithelium involving the omentum is 15:1. This is comparable t o the ratio of benign serous epithelium to endometrioid epithelium in the o mentum, which is 10:1. The ratio of primary peritoneal serous carcinoma to endometrioid carcinoma is 10.5:1. Conclusion. It seems not reasonable that endometrioid carcinoma of the ovar y is 15 times less likely to metastasize to the omentum than its serous cou nterpart. The ratio, however, is not unreasonable if endometrioid and serou s carcinomas arise from preexisting endometrioid or serous epithelium. We c onclude that serous and endometrioid carcinomas may arise primarily in the omentum and, in at least some cases, may derive from their benign counterpa rts. (C) 1999 Academic Press.