Endometriosis generally occurs in the ovary. Intestinal endometriosis is rare. About 1 % of all endometriosis cases become malignant. Malignant transformation of small intestinal endometriosis is very rare. A 55-year-old woman who underwent total abdominal hysterectomy and bilateral salpingo-oophorectomy and omentectomy for endometriosis 7 years ago presented to her primary care doctor with melena. A tumor was detected in the right lower abdomen by ultrasonography. The doctor referred her to our hospital. Computed tomography demonstrated a lobulated tumor ventral to the right common iliac vessels. Magnetic resonance imaging demonstrated that the tumor had heterogeneous intensity on T2-weighted images. Several small cysts with high intensity were observed caudal to the tumor on T2-weighted images. We performed partial small intestinal resection for the lesion. The tumor was diagnosed as endometrioid adenocarcinoma of the small intestine. She has been relapse-free for 5 years after surgery. Only three cases of malignant transformation of small intestinal endometriosis have been reported previously. It is very rare for long-term survival to be obtained with surgery alone, as in our case. This case report highlights the imaging findings for malignant transformation of intestinal endometriosis.
Keywords: Endometriosis; Magnetic resonance imaging; Malignant transformation; Small intestine.