Rhabdomyosarcoma with an intratumoral adult type rhabdomyoma nodule with focal neuronal differentiation - diagnosis, prognosis and treatment of a rare disease

AbstractRhabdomyosarcomas with areas reminiscent of adult type rhabdomyoma are rare and almost exclusive of pretreated tumors. We present a case of 17-year-old patient who sought medical assistance due to a right painless paratesticular mass. At gross examination, the paratesticular mass was a 5 cm tumor (embryonal rhabdomyosarcoma) with a discrete 2.0 cm grayish nodule at the periphery. At microscopy, smaller nodule showed large eosinophilic granular cells suggestive of adult type rhabdomyoma. These cells were strongly and diffusely positive for desmin and multifocally positive for myogenin. Focal neuronal and neural differentiations (NSE and GFAP expression) were also detected. Awareness of benign appearing intratumoral rhabdomyoma in rhabdomyosarcomas of paratestis/retroperitonium is of relevance. Such tumor heterogeneity may be a diagnostic pitfall especially in the scenario of needle biopsies and frozen section consultation.