I have heard that if you see one primary bone tumor in your career, then you’re done. That is a myth. Maybe it’s because I do MSK or more likely, that’s just plain wrong.
Anyway, a great case demonstrating classic features of an unfriendly neoplasm. I’m not saying it isn’t a met or lymphoma but I’d bet Ewing’s sarcoma or chondrosarcoma over osteosarcoma (although I really like it for chondrosarcoma).
My beef with chondrosarcoma is that it’s not “ring and arc”-y enough compared to others but it’s definitely in the considerations.
The fine reticular calcification in the soft tissue mass rather than bone forming periosteal reaction tips the scales for me. That said, there is substantial overlap in the imaging appearances of sarcomas and it primarily depends on the ability to mount a reparative response to the destruction.