Pathology: periosteal osteosarcoma

Periosteal osteosarcoma

• Lobulated; osteo-chondroid neoplasm

• Chondroid matrix: moderately cellular, with polygonal cells arranged in small clusters; eosinophilic cytoplasm; hyperchromatic nuclei, with mild pleomorphism and inconspicuous mitotic activity; patchy enchondral-type ossification

• Osteoid matrix: anastomosing trabeculae of predominantly woven bone; moderately cellular; small epithelioid cells with hyperchomatic nuclei

• FISH: MDM2 non-amplified