Endometriosis may be the pre-malignant lesion for certain histologic subtypes of ovarian cancers

16504 Background: The association of ovarian carcinoma and endometriosis has been suggested but there has been limited analysis of this relationship. Recent studies have shown only a 20–40% correlation of ovarian cancer with endometriosis. The objective of this study was to demonstrate the concurrent findings of endometriosis and ovarian cancer in our diverse population and to investigate if endometriosis is the pre-malignant lesion for certain ovarian cancer subtypes. Methods: Microscopic slides of primary epithelial ovarian cancers resected at the time of hysterectomy and salpingo-oopherectomy from 2000–2005 were reviewed for the presence of endometriosis. Their counterpart paraffin-embedded tissue samples were obtained and used for immunohistochemical staining of several candidate genes and their differential protein expression profiles were recorded. Results: While the overall incidence of epithelial ovarian cancers in Hawaii was comparable to other populations, the incidence of cancer subtypes differed. Serous, endometrioid, and clear cell cancers had similar incidence rates (28%, 29%, and 21% respectively) in our population compared to the general population where serous subtypes predominate (40–50%) and clear cell is found less often (10%). Unlike the general population, clear cell and endometrioid subtypes in our population were associated with endometriosis to a much greater extent (92% and 94%) - the highest correlation seen to date. Mucinous cancers were less commonly associated (67%), while serous carcinomas were rarely associated (6%). There also appeared to be a predilection for age <50 yo with the endometriosis-associated cancers. Finally, examination of different candidate genes revealed discrete expression patterns among the cancer subtypes, mimicked to a lesser extent in their coexisting endometriosis sites. Conclusions: This data represents the first time that endometriosis has been associated with clear cell and endometrioid subtypes to such a profound degree suggesting that endometriosis may indeed be the pre-malignant lesion of certain epithelial ovarian cancer subtypes. Further studies will be needed to elucidate this association fully and examine, if perhaps, ethnicity plays a larger role than previously thought. No significant financial relationships to disclose.