Pathology: desmoplastic small round cell tumour

Desmoplastic small round cell tumour

  • Nests of round cells

  • Scant eosinophilic cytoplasm with indistinct cell borders

  • Monomorphic round nuclei; mitotic activity

  • Intervening fibrous stroma; necrosis

  • IHC: WT-C

  • RNA-seq: EWSR1::WT1 gene fusion

Desmoplastic small round cell tumour

  • Nests of round cells

  • Scant eosinophilic cytoplasm with indistinct cell borders

  • Monomorphic round nuclei; mitotic activity

  • Intervening fibrous stroma; necrosis

  • IHC: desmin, keratin (AE1/AE3)

  • RNA-seq: EWSR1::WT1 gene fusion

Desmoplastic small round cell tumour

  • Nests of polygonal cells

  • Eosinophilic cytoplasm with indistinct cell borders

  • Round nuclei with moderate atypia; mitotic activity

  • Intervening fibrous stroma; necrosis

  • RNA-seq: EWSR1::WT1 gene fusion

Desmoplastic small round cell tumour

  • Sheets of round-epithelioid cells

  • Pale eosinophilic cytoplasm

  • Round-ovoid nuclei; mitotic activity

  • Focal myxoid stroma

  • IHC: desmin

  • RNA-seq: EWSR1::WT1 gene fusion

Desmoplastic small round cell tumour

  • Sheets of round-epithelioid cells

  • Pale eosinophilic cytoplasm

  • Round-ovoid nuclei; mitotic activity

  • Focal myxoid stroma

  • IHC: desmin

  • RNA-seq: EWSR1::WT1 gene fusion

Desmoplastic small round cell tumour

  • Sheets and nests of round cells

  • Scant eosinophilic cytoplasm with indistinct cell borders

  • Monomorphic round nuclei; mitotic activity

  • Intervening fibrous stroma

  • IHC: desmin, keratin (AE1/AE3)

  • FISH: EWSR1-rearrangement