Pathology: malignant peripheral nerve sheath tumour

Sheets and nests of epithelioid-spindle cells

Pale eosinophilic cytoplasm with occasional clearing

Ovoid nuclei with marked pleomorphism; conspicuous mitotic activity

Scant collagenous stroma

IHC: desmin, SOX10, p53

DNA-seq: NF1 exon 28; c.3755T>A (p.Leu1252*) mutation identified

Biphasic; fascicles of spindle cells and gland-forming epithelial cells

Eosinophilic cytoplasm with occasional intracytoplasmic mucin

Ovoid-round nuclei with vesicular chromatin; conspicuous mitotic activity 

Collagenous stroma

Fascicles of spindle cells

Pale amphophilic cytoplasm

Ovoid nuclei with small nucleoli; conspicuous mitotic activity

Interspersed adipocytes and metaplastic bone

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

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

Underlying NF2

Fascicles of spindle-epithelioid cells

Eosinophilic cytoplasm

Round nuclei with small nucleoli and moderate pleomorphism; occasional mitotic activity

NB: background conventional schwannoma

Underlying rhabdoid tumour syndrome

Sheets of epithelioid cells

Amphophilic cytoplasm

Round nuclei with small nucleoli and moderate pleomorphism; conspicuous mitotic activity

IHC: S100, SOX10

Spindle-polygonal cells with amphophilic cytoplasm

Ovoid-round nuclei with mild pleomorphism; occasional mitotic activity

Interspersed rhabdomyoblastic cells with abundant eosinophilic cytoplasm; eccentric nuclei with occasional multinucleation

Abundant myxoid stroma 

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

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

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

Sheets and nests of epithelioid cells; amphophilic cytoplasm with occasional eosinophilic globules

Round-ovoid nuclei with speckled chromatin and mild-moderate pleomorphism; occasional mitotic activity

Areas of prominent neurofibrillary background

IHC: H3K27me3

PMID: 34339532

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