[Primary primitive neuroectodermal tumor of the urinary bladder. Clinicopathologic case report and differential small cell tumor diagnosis of this site].

We report a rare case of primary primitive neuroectodermal tumour of the bladder in an adult. A huge tumour with extensions into pelvic and retroperitoneal tissue was found radiologically in a 62-year-old man. The patient did not complain about remarkable clinical symptoms until 4 days before admission to hospital. Histology of diagnostic transurethral tumour resection showed a small round-cell tumour with focal necrosis and scattered Homer-Wright rosettes. Immunohistochemical analysis revealed that tumour cells stained positively with 013, a monoclonal antibody which recognizes the membrane glycoprotein p30/32MIC2. Focally, tumour cells stained positively for vimentin, NSE, S-100 protein and synaptophysin. The patient died 3 weeks later because of fulminant pulmonary embolism and autopsy revealed a huge, partly exophytic but mainly endophytic tumour of the bladder with extensions into the rectum and retroperitoneal tissue. The differential diagnosis of small round-cell tumours in this location is discussed.