RESUMEN
Primary endometrioid adenocarcinoma of the rectovaginal septum is rare. Its pathogenesis is not clear and there is no standard treatment. One patient with endometrioid adenocarcinoma of the rectovaginal septum arising from deep infiltrative endometriosis was admitted to Qingdao Municipal Hospital. The patient presented with incessant menstruation and abdominal distension. She had bilateral ovarian endometriotic cystectomy 6 years ago. Imaging findings suggested a pelvic mass which might invade the rectovaginal septum. Pathological results of primary surgery confirmed endometrioid carcinoma of the pelvic mass arising from the rectovaginal septum. Then she had a comprehensive staged surgery. Postoperative chemotherapy was given 6 times. No recurrence or metastasis was found during the 2-year follow-up. The possibility of deep infiltrating endometriosis and its malignant transformation should be considered in the differential diagnosis of a new extragonadal pelvic lesion in a patient with a history of endometriosis, which would avoid misdiagnosis and missed diagnosis.