Pathology: perivascular epithelioid cell tumour (PEComa)

Angiomyolipoma

  • Sheets of adipocytes with interspersed nests and fascicles of spindle cells

  • Adipocytes have abundant clear cytoplasm with occasional vacuolation; small eccentric nuclei

  • Spindle cells have eosinophilic cytoplasm; monomorphic ovoid nucleoli with small nucleoli and inconspicuous mitotic activity

  • Interspersed is a prominent ectatic vasculature

  • IHC: Melan-A

Angiomyolipoma

  • Sheets of adipocytes with interspersed nests and fascicles of spindle cells

  • Adipocytes have abundant clear cytoplasm with occasional vacuolation; small eccentric nuclei

  • Spindle cells have eosinophilic cytoplasm; monomorphic ovoid nucleoli with small nucleoli and inconspicuous mitotic activity

  • Occasional ectatic vessels; central dollop of hyalinized collagen

  • IHC: HMB45, Melan-A

PEComa

History of tuberous sclerosis

  • Anastomosing cords of epithelioid cells

  • Amphophilic cytoplasm with indistinct cell borders

  • Round-ovoid nuclei with prominent nucleoli and mild pleomorphism; inconspicuous mitotic activity

  • Intersecting hyalinized fibrovascular septa

  • IHC: smooth muscle actin, desmin, HMB45, Melan-A


PEComa, malignant

  • Spindle cells in fascicles with rare nests of polygonal cells

  • Granular eosinophilic-clear cytoplasm

  • Ovoid nuclei; polygonal cells have hyperchromasia, multilobation and marked pleomorphism; mitotic activity

  • Patchy necrosis

  • IHC: Melan-A

  • RNA-seq: TSC2 SNV (p.Q478)

PEComa

  • Nests and anastomosing cords of epithelioid cells

  • Abundant amphophilic cytoplasm

  • Round-ovoid nuclei with vesicular chromatin, prominent nucleoli and mild pleomorphism; inconspicuous mitotic activity

  • Intersecting fibrovascular septa

  • IHC: Melan-A


PEComa

  • Sheets of epithelioid cells

  • Abundant amphophilic cytoplasm

  • Round-ovoid nuclei with macronucleoli, moderate pleomorphism and occasional multinucleation; mitotic activity

  • Prominent ectatic vasculature

  • IHC: Melan-A

PEComa

  • Sheets of epithelioid-spindle cells

  • Abundant eosinophilic cytoplasm

  • Round-ovoid nuclei with macronucleoli, moderate pleomorphism and occasional multinucleation; mitotic activity

  • Occasional small ectatic vessels

  • IHC: smooth muscle actin, Melan-A