An unusual case of dedifferentiated leiomyosarcoma of the primary mesentery mimicking ovarian cancer.

Dedifferentiated leiomyosarcoma of the primary mesentery is extremely rare. We report a case of dedifferentiated leiomyosarcoma (LMS) of the primary mesentery mimicking ovarian cancer. A 62-year-old woman presented with progressive low abdominal pain. Pelvic magnetic resonance imaging (MRI) revealed a large adnexal mass with carcinomatosis peritonei. Laboratory examination revealed an elevated serum level WBC 46,520/uL (Ref. 4,000~11,000/uL), PLT 687,000/uL (Ref. 140,000~400,000/uL), CA-125 69.1 U/mL (Ref. 0~35 U/mL), and beta-hCG 43.1 mIU/mL (Ref. 0~5 mIU/mL) level. The patient underwent exploratory laparotomy under suspicion of ovarian cancer. We observed a 20-25 cm-sized huge pedunculated subserosal mass arising from the mesentery, and other masses with sizes of 15-20 cm were adherent to peritoneum and ileocecal region. There was a multiple seeding metastasis in the omentum and bowel mesentery. A frozen section revealed malignancy originating from the mesentery, and thus, total abdominal hysterectomy, bilateral salpingo-oophorectomy, omentectomy, pelvic and para-aortic lymph node dissection, and mass excision were performed. Subsequent histopathologic examination resulted in a final diagnosis of dedifferentiated leiomyosarcoma of the mesentery. The patient was transferred to a department of hemato-oncologist for additional managements. Doxorubicin was used for adjuvant chemotherapy.