Pathology: atypical spindle cell / Pleomorphic lipomatous tumour

Hypocellular fascicles of spindle cells with admixed adipocytes

Spindle cells have eosinophilic cytoplasm; nuclei are ovoid with mild-moderate atypia and small nucleoli; mitotic activity is not conspicuous

Adipocytes have abundant clear cytoplasm with occasional multivacuolation and moderate variability in size; nuclei are monomorphic and peripherally located

Abundant myxoid-collagenous stroma

IHC: negative for MDM2, CDK4

Hypocellular spindle cell neoplasm with a patternless distribution

Spindle-stellate cells have dense eosinophilic cytoplasm; the nuclei are round, hyperchromatic and pleomorphic, with frequent multinucleation; there is occasional mitotic activity

Adipocytes have abundant clear cytoplasm with occasional vacuolation; nuclei are monomorphic and peripherally located

Abundant myxoid-collagenous stroma

FISH: MDM2 non-amplified

Variable cellularity; spindle cells with vague fascicular patttern

Spindle-stellate cells with pale eosinophilic cytoplasm

Round-ovoid nuclei with hyperchromasia, multinucleation and pleomorphism; rare mitotic activity

Adipocytes have abundant clear cytoplasm with occasional vacuolation; nuclei are monomorphic and peripherally located

Myxoid-collagenous stroma; chronic inflammation

FISH: MDM2 non-amplified