A case of uterine carcinosarcoma which was strongly suspected to have metastases to the psoas and gluteus muscles.

Metastasis to the skeletal muscles is uncommon. We report a case which was strongly suspected to have psoas and gluteus muscle metastases from uterine carcinosarcoma. A 68-year-old woman (gravida, 2; para, 0) underwent retroperitoneal endoscopic paraaortic lymphadenectomy, laparoscopic modified radical hysterectomy, bilateral salpingo-oophorectomy and pelvic lymphadenectomy for uterine carcinosarcoma, suspected to be stage IB. Metastasis to one right pelvic lymph node was observed. Ascites fluid cytology was negative. Postoperative pathological examination revealed stage IIIC1 (pT1bN1M0) disease. Five cycles of chemotherapy with paclitaxel + carboplatin were performed. 10 months after chemotherapy, serum cancer antigen-125 level was elevated. Computed tomography (CT) revealed a 3-cm tumor of the left psoas muscle and magnetic resonance imaging revealed a tumor of the left gluteus maximus muscle. These lesions showed fluorodeoxyglucose uptake in positron emission tomography-CT. Because we considered the tumors were metastases of uterine carcinosarcoma, we recommended her chemotherapy. However, after one cycle of chemotherapy, the patient underwent immunotherapy elsewhere with immune checkpoint inhibitors. 5 months after the recurrence, she was alive.