A rare case of extrauterine adenosarcoma arising in endometriosis of the rectovaginal septum

Objective To present a rare case of endometrial stromal sarcoma arising in endometriosis of the rectovaginal septum. Design Case report. Setting Academic tertiary referral center for endometriosis treatment. Patient(s) A 50-year-old woman with a history of endometriosis presented with catamenial rectal pain and deep dyspareunia. Imaging findings suggested new endometriotic lesions in the rectovaginal space. Intervention(s) Total hysterectomy, salpingo-oophorectomy, and excision of the lesion in the rectovaginal septum were performed. Although extemporary pathology confirmed endometriosis, the final histologic diagnosis was extrauterine adenosarcoma in the rectovaginal septum. Two years later, recurrence of the malignancy occurred and was treated by resecting the new perirectal mass. Subsequent radiotherapy and chemotherapy were administered. Main outcome measure(s) Imaging findings at follow-up evaluation. Result(s) The patient was in good health for 2 years after the initial surgery, when she developed a new lesion at the site of the previous resection. The histologic appearance of the lesion was consistent with recurrence of the tumor. After postoperative therapy, the patient is now without evidence of disease. Conclusion(s) Malignant transformation of endometriosis should be considered in the differential diagnosis of a new pelvic lesion in a patient with a history of endometriosis.