Pathology: myoepithelial tumour

Myoepithelial tumour

  • Fascicles of spindle-epithelioid cells

  • Pale amphophilic cytoplasm

  • Ovoid-angulated nuclei with small nucleoli and mild atypia; inconspicuous mitotic activity

  • Areas of hyalinized stroma

  • IHC: smooth muscle actin, S100, keratin (AE1/AE3)

  • RNA-seq: EWSR1::PBX3 gene fusion

Myoepithelial tumour

  • Fascicles of spindle-epithelioid cells

  • Pale amphophilic cytoplasm

  • Ovoid nuclei with small nucleoli and mild atypia; inconspicuous mitotic activity

  • Focal cystic degeneration

  • IHC: S100, smooth muscle actin, epithelial membrane antigen

  • RNA-seq: EWSR1::PBX3 gene fusion

Myoepithelial tumour

  • Infiltrative; cellular spindle cell neoplasm with vague storiform-fascicular pattern

  • Eosinophilic cytoplasm

  • Round-ovoid nuclei with prominent nucleoli and mild atypia; brisk mitotic activity

  • Occasional thin and thick-walled vessels, osteoclast-type giant cells, haemosiderin-laden macrophages, and lymphocytes

  • RNA-seq: EWSR1::PBX3 gene fusion

Myoepithelial tumour

  • Spindle-epithelioid cells in fascicles and cords

  • Pale amphophilic cytoplasm

  • Round-ovoid-angulated nuclei with small nucleoli and mild atypia; inconspicuous mitotic activity

  • Intervening bands of hyalinized stroma; occasional thick-walled ectatic vessels with hyalinized walls

  • IHC: calponin, SATB2

  • RNA-seq: EWSR1::PBX3 gene fusion

Myoepithelial tumour

  • Infiltrative; spindle cell fascicles

  • Pale amphophilic cytoplasm with delicate bipolar processes

  • Ovoid-angulated nuclei with small nucleoli and mild atypia; inconspicuous mitotic activity

  • Intervening bundles of thin collagen fibres; focal myxoid stroma; vessels with hyalinized walls; occasional plugs of lymphocytes in lymphovascular spaces

  • RNA-seq: EWSR1::POU5F1 gene fusion

Myoepithelial tumour

  • Cords and nests of epithelioid cells

  • Abundant eosinophilic cytoplasm; areas with clear cytoplasmic vacuolation

  • Round-ovoid nuclei with mild atypia; inconspicuous mitotic activity

  • Intervening broad bands of hyalinized stroma

  • RNA-seq: FUS::KLF17 gene fusion

Myoepithelial tumour

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

  • Pale amphophilic cytoplasm with delicate tapering processes

  • Ovoid-angulated nuclei with small nucleoli and mild atypia; occasional mitotic activity

  • Intervening myxoid-collagenous stroma; long wavy thin-walled vessels

  • IHC: S100, SOX10, keratin (AE1/AE3)

  • RNA-seq: IRF2BP2::CDX1 gene fusion


Myoepithelial tumour

  • Circumscribed; short spindle cell fascicles

  • Pale amphophilic cytoplasm

  • Ovoid-angulated nuclei with small nucleoli and mild atypia; inconspicuous mitotic activity

  • Interspersed thick collagen bands; prominent hyalinized vessels

  • RNA-seq: EWSR1::POU5F1 gene fusion


Myoepithelial tumour

  • Infiltrative; short fascicles of spindle-ovoid cells

  • Pale amphophilic cytoplasm

  • Ovoid nuclei with frequent clefts, small nucleoli and mild atypia; mitotic activity

  • Background of plump spindle cells with more abundant eosinophilic cytoplasm; microcystic degeneration

  • RNA-seq: EWSR1::ZNF444 gene fusion