Pathology: embryonal rhabdomyosarcoma

Rhabdomyosarcoma, embryonal

• Fascicles of spindle-polygonal cells

• Scant amphophilic cytoplasm

• Round-ovoid hyperchromatic nuclei with moderate pleomorphism

• Scattered rhabdomyoblasts with brightly eosinophilic cytoplasm and eccentric nuclei

• RNA-Seq: DICER1 mutation (pD1709N)

Rhabdomyosarcoma, embryonal

• Sheets of spindle-polygonal cells

• Scant pale eosinophilic cytoplasm

• Round-ovoid hyperchromatic nuclei with moderate pleomorphism

• Scattered rhabdomyoblasts with brightly eosinophilic cytoplasm and eccentric nuclei

• IHC: desmin, myogenin

Rhabdomyosarcoma, embryonal

Young adult; testis

• Sheets of spindle and round-polygonal cells 

• Scant pale eosinophilic cytoplasm

• Round-ovoid nuclei with moderate pleomorphism 

• Rhabdomyoblasts with brightly eosinophilic cytoplasm, occasional cross-striation, and frequent multinucleation

• IHC: desmin, MDM2, H3K27me3

• FISH: positive for MDM2-amplification

Rhabdomyosarcoma, embryonal

Adolescent; paratesticular

• Sheets of polygonal-spindle cells

• Scant amphophilic cytoplasm

• Round-ovoid nuclei with mild pleomorphism; conspicuous mitotic activity

• Rare epithelioid-rhabdoid cells with abundant eosinophilic cytoplasm; eccentric nuclei

• RNA-seq: negative for FOXO1-rearrangement

Rhabdomyosarcoma, embryonal

• Loose fascicles of spindle-epithelioid cells; condensation below epithelial structures ("botryoides")

• Bright eosinophilic cytoplasm with long tapering processes; conspicuous "cross-striations"

• Peripheral nuclei with mild atypia, prominent nucleoli, and occasional multinucleation; occasional mitotic activity

• Scattered round-polygonal cells with scant cytoplasm; round nuclei with mild pleomorphism

• RNA-seq: negative for FOXO1-rearrangement

Rhabdomyosarcoma, embryonal

Adolescent; paratesticular

• Loose fascicles of spindle cell

• Eosinophilic cytoplasm with long tapering processes; occasional "cross-striations"

• Round-ovoid nuclei with mild-moderate pleomorphism; conspicuous mitotic activity

• Scattered epithelioid cells with abundant eosinophilic cytoplasm; eccentric nuclei

• IHC: desmin, myogenin, MDM2

• RNA-seq: negative for FOXO1-rearrangement

Rhabdomyosarcoma, embryonal

Adolescent; paratesticular

• Sheets of spindle-epithelioid cell

• Amphophilic cytoplasm with occasional delicate tapering processes

• Round-ovoid nuclei with moderate pleomorphism; conspicuous mitotic activity

• Focal myxoid stroma; necrosis

• RNA-seq: negative for FOXO1-rearrangement