OP30.10: Extrauterine undifferentiated endometrioid stromal sarcoma arising in endometriosis of the rectovaginal septum of a postmenopausal patient with recent onset of pelvic pain

To present a rare case of endometrial stromal sarcoma arising in endometriosis of the rectovaginal septum. A 57-year-old postmenopausal woman with no apparent previous history of endometriosis presented with recent onset of pelvic pain. Transvaginal ultrasonography suggested the presence of three lesions in the rectovaginal space compatible with the ultrasonographic appearance of deep endometriosis: These were located in the vaginal fornix (8x8x8x9 mm), in the left utero-sacral ligament (17x7x10 mm) and occluding the pouch of Douglas (17x1x15 mm). In addition there was a 26 mm isthmic posterior uterine fibroid. Because of the persistence of pelvic pain after treatment with non-steroidal ant-inflammatory drugs, a total hysterectomy with salpingo-oophorectomy and excision of the rectovaginal lesions was performed. In retrospect, on comparison of the present findings with ultrasonographic typical images of deep endometriotic lesions both appeared very similar. The final histologic diagnosis was extrauterine undifferentiated endometrioid stromal sarcoma close to co-existing deep endometriosis in the rectovaginal septum and myometrium (adenomyosis). Subsequent radiotherapy was administered. Seven months after the initial surgery the patient is in good health. Malignant transformation of deep endometriosis should be considered in the differential diagnosis of pelvic lesions even in a patient without a history of endometriosis but sudden onset of pelvic pain and ultrasonographic signs of deep endometriosis. However, currently it is not possible to predict malignant transformation by ultrasonography. This is why multiple laparoscopic biopsies and regular follow-up by ultrasound is warranted.