Pathology: malignant peripheral nerve sheath tumour

Malignant peripheral nerve sheath tumour

  • Underlying NF1

  • Multinodular with "marbled" pattern (variable cellularity)

  • Spindle-epithelioid cells with pale amphophilic cytoplasm

  • Ovoid-round nuclei with moderate pleomorphism; conspicuous mitotic activity

  • Scant myxoid stroma

  • IHC: H3K27me3

Malignant peripheral nerve sheath tumour

  • Underlying NF1

  • "Marbled" pattern (variable cellularity)

  • Spindle-epithelioid cells with pale amphophilic cytoplasm

  • Ovoid-round nuclei with moderate pleomorphism; conspicuous mitotic activity

  • Intervening collagenous-myxoid stroma

  • IHC: S100

Malignant peripheral nerve sheath tumour, with rhabdomyoblastic differentiation (malignant Triton tumour)

  • Underlying NF1

  • Peritheliomatous pattern

  • Spindle-polygonal cells with amphophilic cytoplasm

  • Ovoid-round nuclei with marked pleomorphism; conspicuous mitotic activity

  • Small clusters of rhabdoid cells with abundant eosinophilic cytoplasm; eccentric nuclei with occasional multinucleation

  • Abundant myxoid stroma

  • IHC: myogenin, H3K27me3

Malignant peripheral nerve sheath tumour, with rhabdomyoblastic differentiation (malignant Triton tumour)

  • Fascicles of spindle cells with pale amphophilic cytoplasm

  • Ovoid-round nuclei with moderate pleomorphism; conspicuous mitotic activity

  • Interspersed nests of rhabdoid cells with abundant eosinophilic cytoplasm; eccentric round nuclei with macronucleoli

  • IHC: myogenin, H3K27me3

Malignant peripheral nerve sheath tumour, with rhabdomyoblastic differentiation (malignant Triton tumour)

  • Short fascicles of spindle cells

  • Pale amphophilic cytoplasm

  • Ovoid-round nuclei with coarse chromatin and moderate pleomorphism; conspicuous mitotic activity

  • Epithelioid cells centred around vessels; patchy necrosis

  • IHC: desmin, myogenin, H3K27me3

Malignant peripheral nerve sheath tumour, with differentiation mesenchymal (cartilaginous) differentiation

  • Biphasic with spindle cell and chondroid components

    • Spindle cells: herringbone pattern; pale amphophilic cytoplasm; ovoid nuclei with mild-moderate pleomorphism; conspicuous mitotic activity

    • Cartilage: hypo-moderately cellular lobules of stellate-polygonal cells; pale eosinophilic cytoplasm; round hyperchromatic nuclei with mild pleomorphism; rare mitotic activity; abundant hyaline cartilage matrix with myxoid degeneration

  • IHC: H3K27me3, S100, SOX10

  • RNA-seq: negative

  • ISBN: 978-1-933477-30-5