Nonepithelial neoplasms of the urinary bladder.

Nonepithelial tumors are rare in the urinary bladder, but their exact classification is very important in the differential diagnosis between these tumors and epithelial lesions. In the new WHO classification and in the third series of the Armed Forces Institute of Pathology (AFIP) "Atlas of Tumor Pathology" on urinary bladder tumors, various mesenchymal tumors, mixed epithelial and mesenchymal tumors and myofibroblastic proliferations are summarized. In the following we will describe the histology, immunohistology, and cytogenetics of nonepithelial tumors and lesions.