Sato et al (2000) showed that in three out of five ovarian carcinomas associated with endometriosis, LOH at 10q23.3 occurs in both the carcinoma and in endometriotic lesions, implicating that LOH is an early event in carcinogenesis and that PTEN is involved in the progression from endometriotic precursor lesion to clear cell or endometrioid ovarian cancer. The gene discussed is PTEN; the disease is endometriosis.