Pseudosarcomatous and sarcomatous proliferations of the bladder.

Pseudosarcomatous fibromyxoid tumor (PFT), postoperative spindle cell nodule (PSN), sarcoma, and sarcomatoid carcinoma of the bladder are frequently difficult to distinguish histopathologically with significant differences in disease-related outcomes. A retrospective review of our pathology registry over the last 25 years identified 7 PFT, 10 PSN, 18 primary bladder sarcomas, and 17 sarcomatoid carcinomas. Most patients with PFT, PSN, sarcoma, and sarcomatoid carcinoma were diagnosed between the ages of 50 to 60 years with PFT and PSN most commonly detected in women. A previous history of urological instrumentation and bladder cancer was present in all patients with PSN but none of the patients with PFT. Pseudosarcomatous fibromyxoid tumors were characterized by a tissue culture-like proliferation of myofibroblastic cells with focal atypia and overall cytoarchitectural features mimicking nodular fasciitis. Sarcomas and sarcomatoid carcinomas exhibited cellular atypia, mitotic activity with atypical mitosis, and the presence of necrosis. Transurethral resection was sufficient to control all PFT and PSN with no evidence of distant metastatic spread. In contrast, local recurrences and distant metastases frequently occurred in patients with primary sarcoma and sarcomatoid carcinoma despite aggressive surgical management, which was often combined with neoadjuvant chemotherapy (50% and 65% disease-specific mortality, respectively). Pseudosarcomatous fibromyxoid tumor and PSN have unique clinical and pathologic features that allow their distinction from primary bladder sarcoma and sarcomatoid carcinoma.