Lack of proliferative activity of surface epithelial inclusion cysts of the ovary

Surface epithelial inclusion cysts (SEICs) of the ovary are epithelial inclusions in the ovarian cortex believed to form from invagination of the surface epithelium at the time of ovulation. It has long been theorized that SEICs are related to the development of epithelial ovarian cancer. Ki-67 antigen is a marker of cell proliferation and has been shown to be prognostic in epithelial ovarian cancer. The purpose of this study was to evaluate Ki-67 activity in SEICs to evaluate their possible connection to ovarian neoplastic proliferation. A retrospective review of benign ovaries removed at the time of pelvic surgery was performed. Slides were immunostained with Ki-67. Proliferation index, expressed as the percent of cells staining in SEICs, was calculated. Proliferative activity was scored as negligible, low, moderate, or high, at <5%, 5-10%, 11-40%, and >40%, respectively. Eighteen ovaries from 18 women were evaluated. The percentage of Ki-67 positive cells ranged from 0% to 7%. Ki-67 activity in SEICs of the ovary is negligible to low. Proliferative activity as assessed by Ki-67 staining does not explain any possible relationship of SEICs to epithelial ovarian cancer.