Evaluation of PTEN and Ki67 Expression in Typical and Atypical Endometriosis and Endometriosis Associated Ovarian Cancer

Background: Several studies reported that endometriosis is associated with an increased risk of ovarian cancer. Atypical endometriosis is common in patients with endometriosis-associated ovarian, which might be considered as a precancerous lesion. Objectives: This study aimed to assess ki67 and PTEN expression in endometriosis associated ovarian cancer (EAOC), atypical endometriosis, and typical endometriosis. Methods: In this study, all H & E slides of 260 ovarian endometriosis cases were reviewed. an‎d 25 cases were diagnosed with atypical endometriosis. Forty-one typical endometrioses and 24 ovarian cancers with endometriosis were included. We assessed PTEN and Ki67 immunoexpression in epithelial and stromal cells. Results: The prevalence of atypical endometriosis was about 9%. PTEN loss was found in 12 (out of 24 or 50%) of EAOC, 2 (out of 25; 8%) of atypical endometriosis, and none of the typical endometriosis. In all 12 PTEN loss cases, the PTEN loss pattern in endometriosis adjacent to ovarian cancer was similar to that of ovarian cancer. A total of 7.3% of typical endometriosis and 8% atypical endometriosis and 33.3% of EAOC had Ki67 staining in more than 50% of the epithelial component. Both typical and atypical endometriosis showed similar PTEN loss and Ki 67 staining (in more than 50% of the epithelial component) (P value > 0.05), and both of them were different from EAOC (P value < 0.05). Conclusions: The PTEN loss pattern in endometriosis adjacent to ovarian cancer was similar to that of ovarian cancer. The result indicated that PTEN loss could be an early event in the tumor development pathway from endometriosis to ovarian cancer.