Paratesticular rhabdomyosarcoma presenting as thickening of the tunica vaginalis

Pediatric paratesticular primary malignant tumors are rare, and most of them correspond to rhabdomyosarcomas (RMS). Paratesticular RMS has a better prognosis than RMS originating in other locations, because of its favorable histology and possible early diagnosis. The diagnosis relies upon the US findings of a paratesticular hypervascular mass in an adequate clinical setting. We report the unusual appearance of an infiltrating RMS tumor in a 3-year-old boy. The tumor presented as thickening of the tunica vaginalis. Atypical US appearance and discordance with clinical features caused suspicion of a tumoral process, allowing early diagnosis and treatment.