PAraosteal osteosarcoma

A multilocular fluid intensity peripherally enhancing, centrally cystic/necrotic intramuscular mass lesion measuring about 5.8 x 4.6 x 2.4 cm is noted involving the vastus  lateralis muscle at middle third of thigh demonstrating thin rim of ossification on CT sections with mild focal thickening of underlying lateral femoral cortex – of concern for periosteal osteosarcoma versus bizarre paraosteal osteochondromatous proliferation (BPOP) versus myositis ossificans .

 No evidence of fluid – fluid levels. No evidence of flow voids in the vicinity.

 The mass is based along the lateral few oral cortex. No evidence of reactive bone marrow edema or bony erosion.