Pathology: solitary fibrous tumour

Solitary fibrous tumour

  • Circumscribed; regions of hyper- and hypo-cellularity; spindle cells with patternless architecture

  • Scant pale eosinophilic cytoplasm

  • Monomorphic ovoid nuclei with pin-point nucleoli; inconspicuous mitotic activity

  • Interspersed thick collagen bands; ectatic and branching vessels, some with hyalinized walls

  • IHC: STAT6

  • RNA-seq: NAB2::STAT6 gene fusion

Solitary fibrous tumour

  • Circumscribed; regions of hyper- and hypo-cellularity; spindle cells with patternless architecture

  • Scant pale eosinophilic cytoplasm

  • Monomorphic ovoid nuclei with pin-point nucleoli; inconspicuous mitotic activity

  • Interspersed thick collagen bands; ectatic and branching vessels, some with hyalinized walls

  • IHC: CD34, STAT6

  • RNA-seq: NAB2::STAT6 gene fusion

Solitary fibrous tumour

  • Circumscribed; regions of hyper- and hypo-cellularity; spindle cells with patternless architecture

  • Scant pale eosinophilic cytoplasm

  • Monomorphic ovoid nuclei with pin-point nucleoli; inconspicuous mitotic activity

  • Interspersed thick collagen bands; ectatic and branching vessels, some with hyalinized walls

  • IHC: CD34

  • RNA-seq: NAB2::STAT6 gene fusion

Solitary fibrous tumour

  • Circumscribed; cellular; spindle cells with fascicular-storiform pattern

  • Scant pale eosinophilic cytoplasm

  • Monomorphic ovoid nuclei with pin-point nucleoli; inconspicuous mitotic activity

  • Inconspicuous vasculature; thin wispy collagen fibres

  • IHC: STAT6

  • RNA-seq: NAB2::STAT6 gene fusion

Solitary fibrous tumour, metastatic

  • Circumscribed; cellular; spindle cells with patternless architecture

  • Eosinophilic cytoplasm

  • Ovoid-elongated nuclei with scattered pleomorphism and multinucleation; occasional mitotic activity

  • Occasional thin branching vessels

  • IHC: STAT6, CD34

  • RNA-seq: NAB2::STAT6 gene fusion

Solitary fibrous tumour

  • Circumscribed; cellular; spindle cells with patternless architecture

  • Eosinophilic cytoplasm with vacuolation

  • Monomorphic ovoid nuclei; inconspicuous mitotic activity

  • Occasional thin branching vessels with hyalinized walls

  • IHC: CD34, STAT6

  • RNA-seq: LRP1::STAT6 gene fusion*

* To date unreported in literature

Solitary fibrous tumour, cellular

  • Cellular; epithelioid cells with patternless architecture

  • Scant eosinophilic cytoplasm

  • Monomorphic ovoid nuclei with prominent nucleoli; occasional mitotic activity

  • Small ectatic thin-walled vessels

  • IHC: STAT6

  • RNA-seq: NAB2::STAT6 gene fusion

Solitary fibrous tumour, cellular

  • Cellular; spindle cells with storiform pattern

  • Scant pale amphophilic cytoplasm

  • Monomorphic ovoid nuclei with pin-point nucleoli; inconspicuous mitotic activity

  • Small ectatic thin-walled vessels

  • IHC: CD34, STAT6

  • RNA-seq: NAB2::STAT6 gene fusion

Solitary fibrous tumour, hypocellular

  • Circumscribed; hypocellular; spindle cells in vague fascicles

  • Scant pale eosinophilic cytoplasm

  • Monomorphic elongated ovoid nuclei; inconspicuous mitotic activity

  • Abundant thick bundles of collagen comprised of numerous delicate collagen fibres

  • Small ectatic thin-walled vessels

  • IHC: STAT6

  • RNA-seq: NAB2::STAT6 gene fusion

Solitary fibrous tumour, lipomatous

  • Circumscribed; hypocellular; spindle cells in vague fascicles

  • Scant pale eosinophilic cytoplasm

  • Monomorphic elongated ovoid nuclei; inconspicuous mitotic activity

  • Abundant thick bundles of collagen comprised of numerous delicate collagen fibres

  • Interspersed mature adipocytes

  • IHC: STAT6

  • RNA-seq: NAB2::STAT6 gene fusion

Solitary fibrous tumour, lipomatous

  • Cellular; spindle cells with patternless distribution

  • Scant eosinophilic cytoplasm

  • Monomorphic ovoid nuclei with pin-point nucleoli; inconspicuous mitotic activity

  • Interspersed adipocytes, including some with vacuolated cytoplasm

  • IHC: STAT6

  • RNA-seq: NAB2::STAT6 gene fusion

Solitary fibrous tumour, myxoid

  • Hypocellular; spindle-stellate cells with patternless distribution

  • Abundant eosinophilic cytoplasm

  • Ovoid nuclei with mild atypia and pin-point nucleoli; inconspicuous mitotic activity

  • Prominent myxoid stroma; extracellular myxoid pools

  • IHC: STAT6

  • RNA-seq: NAB2::STAT6 gene fusion

Solitary fibrous tumour, dedifferentiated

  • Cellular; epithelioid cells with peritheliomatous pattern

  • Scant eosinophilic cytoplasm with inconspicuous cell borders

  • Ovoid nuclei with mild pleomorphism; conspicuous mitotic activity

  • Extensive necrosis

  • IHC: STAT6, keratin (AE1/AE3)

  • RNA-seq: NAB2::STAT6 gene fusion