Nonepithelial neoplasms of the urinary bladder

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