Malignant solitary fibrous tumor of the urinary bladder progressing to widespread metastases and death: a rare case report and literature review.

Solitary fibrous tumor (SFT) of the urinary bladder has been rarely reported and malignant bladder SFT is even rarer. Here we present a case of an African-American male with SFT of the urinary bladder (intermediate risk) initially treated by cystoprostatectomy at the age of 59 years. Eight years later, he developed recurrence with widespread metastases to the liver, lungs, and abdominal cavity. He then received temozolomide and bevacizumab with good disease control. However, treatment was paused due to declining performance status. Follow-up at 1 year demonstrated growth of the metastatic lesions. Despite restarting therapy, the patient expired, 11 years after the original diagnosis. Autopsy was performed and revealed widespread metastases within the abdominal cavity (abdominal sarcomatosis) as well as liver, bilateral lung, and diaphragmatic involvement. The cause of death was determined to be metastatic SFT. A comprehensive literature review was performed. Although SFTs are commonly considered benign, a subset of SFTs of the urinary bladder behave aggressively. Risk assessment and proper follow-up for recurrence and metastasis is necessary. The patient was also found at autopsy to have two gastrointestinal stromal tumors (GISTs) in the stomach and near the gastroesophageal junction. To the best of our knowledge, this is the first reported case of a primary urinary bladder SFT resulting in death or having concurrent, multifocal GISTs, and only the second case of a bladder SFT that developed metastases after the initial diagnosis.