Pathology: intra-osseous rhabdomyosarcoma

Intra-osseus rhabdomyosarcoma

  • Fascicles of spindle-epithelioid cells

  • Eosinophilic cytoplasm

  • Round-ovoid nuclei with minimal pleomorphism; inconspicuous mitotic activity

  • Occasional large epithelioid cells with abundant eosinophilic cytoplasm; delicate thin-walled vasculature

  • IHC: desmin, myogenin

  • RNA-seq: MEIS1-NCOA2 gene fusion

  • PMID: 30720533

Intra-osseus rhabdomyosarcoma

  • Short fascicles of spindle-epithelioid cells

  • Amphophilic cytoplasm

  • Eccentric round-ovoid nuclei with mild pleomorphism; mitotic activity

  • IHC: desmin, myogenin, ALK

  • RNA-seq: FUS-TFCP2 gene fusion

  • PMID: 32556562

ALK overexperession may be exploited therapeutically (PMID: 31965718)