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