Epithelial cells in peritoneal fluid—of endometrial origin?

Objective: Our purpose was to examine the immunohistochemical properties of epithelial cells in peritoneal fluid and to compare the staining characteristics with cells of endometrium, menstrual effluent, peritoneum, and endometriotic lesions. Study Design: Samples of menstrual effluent, endometrium, and peritoneal fluid and biopsy specimens of endometriotic lesions and peritoneum from 16 patients were examined. Monoclonal antibodies against vimentin, cytokeratin 18 and 19, and the monoclonal antibody BW495/36, staining an epithelial marker present in endometrium and absent in peritoneal epithelium, were used. Results: All but one sample of menstrual effluent and peritoneal fluid cells stained positively with antibodies against vimentin and cytokeratin 18 and 19. BW495/36 stained 14 of 16 menstrual effluent samples and nine of 16 peritoneal fluid cell samples. Endometriotic specimens showed staining with all markers. No major differences in staining properties were observed in menstrual effluent, endometrium, and peritoneal fluid cells between patients with or without endometriosis. Conclusion: These results support the contention of transport of menstrual detritus to the peritoneal cavity in women with patent fallopian tubes.