Introduction/Background Endometriosis appears to be associated with some epithelial ovarian cancers (EOC).The types that are specially associated are clear cell carcinoma and endometrioid carcinoma.The risk of malignant transformation of endometriosis has been estimated at 1% for premenopausal women and 1–2.5% or postmenopausal women.Endometriosis-associated EOC appears to appear in younger women and has a better prognosis than primary EOC.

Methodology We present the clinical case of a 36-year-old woman,gravida 0,with endometriosis as the only personal history of interest. She came to the emergency room because of rectal bleeding. In the physical examination a pelvic mass of about 9 cm in the rectovaginal septum was found.Abdominal sonography, CT-Scan, MRI and PET-CT were performed. They showed a left pararectal heterogeneous mass measuring 90 mm of maximum diameter. Some small locoregional adenopathies were found, predominantly in the left para-aortic area. The levels of tumoral markers were 1694 mUI/ml for Ca125 and 241 UI/ml for Ca15.3.The first suspected diagnosis based on the imaging findings was a GIST-tumour.However, an endoscopic ultrasonography and fine needle aspiration showed an adenocarcinoma of müllerian origin.Our tumour board committee formed by oncological gynecologists, medical oncologist, radiotherapists and pathologist decided to perform a cytorreductive surgery.A frozen section confirmed it was a malignant tumour,so a complete excision of the mass with hysterectomy,bilateral adnexectomy and rectal resection was performed.The patient received six cycles of Carboplatin/Paclitaxel as adjuvant treatment.

Results The pathological report diagnosed a high grade müllerian adenocarinoma with areas of clear cell differentiation.There was no lymphovascular invasion. Rectosigma was infiltrated. Uterus and ovaries were free of tumoural invasion.

After 18 months of follow-up no recurrence of the disease has been detected.

Conclusion This is a rare case of a carcinoma of Müllerian origin that appeared in the rectovaginal septum in a young woman with endometriosis hystory. In these cases,primary surgery should be the first option of choice as long as complete debulking can be achieved.

Disclosure Nothing to disclose.