A 68-year-old Japanese man was referred to Tsukuba University Hospital for bladder cancer treatment. He had undergone a transurethral resection of a bladder tumor (TURBT) at a local hospital, but the pathological specimen did not contain muscle layer. Abdominal computed tomography (CT) and magnetic resonance imaging revealed a 3 cm non-papillary bladder tumor with muscle invasion, but there was no apparent calcification. The patient underwent re-TURBT at our hospital for diagnosis and staging. A non-papillary pedunculated tumor was identified in the bladder dome, and it contained a small papillary part. The non-papillary part was stony hard and difficult to cut with electrocautery, whereas the small papillary part was easily cut. Histologically, the non-papillary part was composed of sarcomatous elements including osteosarcoma, chondrosarcoma, and spindle cell sarcoma. The papillary part was composed of high-grade urothelial carcinoma and spindle cell sarcoma. Muscularis propria was not present in the specimen. Since the staging study with CT was negative for metastases, we performed a total cystectomy with an ileal conduit under the clinical diagnosis of muscle-invasive sarcomatoid urothelial carcinoma. The pathological findings were identical to those of the re-TURBT specimens, and our diagnosis was pTxN0 sarcomatoid urothelial carcinoma. The patient received adjuvant chemotherapy with two courses of gemcitabine and cisplatin. There was neither recurrence nor metastases during the 20-month follow-up. Reports of sarcomatoid urothelial carcinoma of the bladder with an osteosarcoma element are rare, and only eight other cases hane been reported in the Japanese literature.
Keywords: Bladder tumor; Osteosarcoma; Sarcomatoid variant; Urothelial carcinoma.