Genitourinary tract is the second most common site for rhabdomyosarcomas (RMS). In the Intergroup Rhabdomyosarcoma Study series, about 25% of all RMS arose in this region. The vast majority of these tumors arise in the paratesticular region of adolescents. Most of them are of embryonal type (approx. 93%); the rest are mixed embryonal/alveolar, embryonal/pleomorphic, or pure alveolar type.About 70% of embryonal RMS in paratesticular region show classic morphology (shown in this image) with areas of variable cellularity composed of poorly differentiated tumor cells and varying number of rhabdomyoblasts. The remaining 30% of embryonal RMS show spindle cell morphology - a variant with better prognosis (in children) described in later images.