Primary endometrioid carcinoma of the uterosacral ligament arising from deep infiltrating endometriosis 6 years after bilateral salpingo-oophorectomy due to atypical proliferative endometrioid tumor of the ovary: a rare case report

BACKGROUND: Endometriosis can potentially lead to the development of a malignant tumor. Most malignant tumors arising from the endometriosis originate from the ovarian endometrioma, whereas those arising from extragonadal lesions are rare. We report a rare case of endometrioid carcinoma that developed from deep infiltrating endometriosis in the uterosacral ligament 6 years after treatment for atypical proliferative endometrioid tumor of the ovary in a 48-year-old woman. CASE PRESENTATION: Six years ago, the patient underwent laparoscopic bilateral salpingo-oophorectomy for her right ovarian tumor with atypical proliferative (borderline) endometrioid tumor accompanied by ovarian endometrioma. The solid tumor in the cul-de-sac was detected during follow-up using magnetic resonance imaging. Positron emission tomography/computed tomography revealed an abnormal accumulation of (18)F-fluorodeoxyglucose at the tumor site. Thus, tumor recurrence with borderline malignancy was suspected. The patient underwent diagnostic laparoscopy followed by hysterectomy and partial omentectomy. Retroperitoneal pelvic lymphadenectomy and para-aortic lymphadenectomy were also performed. The cul-de-sac tumor at the left uterosacral ligament was microscopically diagnosed as invasive endometrioid carcinoma arising from deep infiltrating endometriosis. The final diagnosis was primary stage IIB peritoneal carcinoma. The patient received six courses of monthly paclitaxel and carboplatin as adjuvant chemotherapy. The patient showed no evidence of recurrence for 2 years after the treatments. CONCLUSION: This study reports a rare case of metachronous endometriosis-related malignancy that developed 6 years after treatment for borderline ovarian tumor. If endometriosis lesions remain after bilateral salpingo-oophorectomy, the physician should keep the malignant nature of endometriosis in mind.