Epithelial abnormalities in cystic ovarian endometriosis.

To evaluate the prevalence of epithelial abnormalities in cystic ovarian endometriosis. In this observational study, the specimens of 388 consecutive patients undergoing a surgical procedure whose final diagnosis included cystic ovarian endometriosis were histopathologically reviewed. The prevalence and patient characteristics of cases featuring epithelial metaplasia, hyperplasia, atypia, and endometrioid carcinoma arising in endometriosis were analyzed. The epithelial lining was evaluable in 339 cases. Left-sided cysts were significantly more common than right-sided ones (P < 0.0001). The observed prevalence was 12.1% for metaplasia, 9.4% for hyperplasia, 5.9% for atypia, and 4.1% for endometrioid carcinoma arising in endometriosis. Complex hyperplasia, but not simple hyperplasia or metaplasia, was significantly more common in cases with associated endometrioid carcinoma than in all other cases (P < 0.00001). A statistically significant trend for increasing age from normal epithelium to carcinoma was observed (P < 0.001). Epithelial abnormalities are a common finding in cystic ovarian endometriosis. Despite their clinical significance being still debated, complex hyperplasia and atypia can be associated with malignant transformation of endometriosis. Their observation in a surgical specimen, particularly in older patients, should indicate a careful examination of the entire lining of the cyst and a strict follow-up of the patient.