Primary retroperitoneal Müllerian adenocarcinoma arising from endometriosis

Primary retroperitoneal Müllerian adenocarcinoma (PRMA) is an extremely rare tumor and the cause remains unknown. We report a case of PRMA arising from endometriosis. A 52-year-old woman with a history of malignant lymphoma underwent a follow-up computed tomography scan, which revealed a retroperitoneal tumor. Immunohistochemical analysis of tumor resected during laparoscopic surgery showed adenocarcinoma positive for cytokeratin 7 and negative for cytokeratin 20. The patient had undergone hysterectomy and bilateral salpingo-oophorectomy 14 years ago for myoma uteri and endometrial cysts and was treated with estrogen-replacement therapy. The size of the tumor increased and laparotomy was performed. Histopathological examination showed adenocarcinoma resembling endometrial adenocarcinoma, which stained positive for cancer antigen 125, cancer antigen 19-9, estrogen receptor, and progesterone receptor immunohistochemically. The focus of the endometriosis was found at the edge of the tumor, and the stromal cells around the tumor cells were CD10 positive. The patient was diagnosed as having PRMA arising from endometriosis, and treated with adjuvant chemotherapy.