Florid polypoid endometriosis exacerbated by tamoxifen therapy in breast cancer

BACKGROUND: We report an unusual case where tamoxifen may have exacerbated the growth of multiple polypoid endometriotic implants. CASE: A premenopausal woman with right breast intraductal carcinoma underwent modified radical mastectomy and received six courses of chemotherapy, followed by continuous oral tamoxifen. Irregular vaginal bleeding was noted 5 years after the mastectomy and transvaginal ultrasound detected a 6-cm cul-de-sac mass. The serum CA 125 level was 138.86 U/mL. Surgical pathology showed florid polypoid endometriosis over the resected rectal segment and endometriotic implants over multiple biopsy sites of the peritoneal surface. CONCLUSION: The estrogenic effects of tamoxifen may have induced florid endometriosis in this hypoestrogenic woman. If breast cancer patients have preexisting endometriosis, adjuvant hormonal therapy other than tamoxifen should be considered.