Young adult; paratesticular
Nests and fascicles with heterogeneous composition
Fascicles of spindle-rhabdoid cells with abundant eosinophilic cytoplasm; conspicuous cross striations; round-ovoid nuclei with mild atypia and occasional multi-nucleation; inconspicuous mitotic activity; occasional myotube-like structures
Sheets of small round cells with scant cytoplasm; round nuclei with mild atypia; conspicuous mitotic activity
Interspersed ganglion-type cells; abundant cytoplasm with occasional Nissl substance; central nuclei with macronucleoli
IHC: myogenin, synaptophysin
Frequent HRAS mutations (PMID: 26872011)