Sarcopedia

Classified as Ewing-like sarcoma - shares histological and some clinical features with Ewing sarcoma BCOR FISH or RT-PCR required for definitive diagnosis Treated with Ewing sarcoma protocols pending more specific data Molecular characterisation revolutionised classification of small round cell sarcomas

WWTR1-CAMTA1 FISH is diagnostic - present in vast majority Multifocal presentation common - staging must assess all sites Indolent disease may be observed; intervention for progressive lesions Hepatic transplantation considered for localised multifocal hepatic disease Sirolimus, sorafenib, bevacizumab for progressive metastatic disease

FOS rearrangements are diagnostic - distinct from epithelioid angiosarcoma Eosinophilia in peripheral blood and inflammatory infiltrate in tissue are characteristic Must be distinguished from epithelioid angiosarcoma and epithelioid haemangioendothelioma Simple excision is curative in most cases

Small round blue cell tumour of Bone in a child/adolescent EWSR1-FLI1 fusion is pathognomonic Onion-skin periosteal reaction on XR Multimodal treatment: chemo + surgery ± radiotherapy

Now considered largely synonymous with undifferentiated pleomorphic sarcoma per WHO 2020 Must rule out other pleomorphic sarcomas with differentiation (dedifferentiated liposarcoma, etc.) MDM2 FISH and immunohistochemistry helpful to exclude dedifferentiated liposarcoma

Benign heterotopic ossification Wait for maturation before surgical excision NSAIDs helpful for prevention