Pathology: periosteal osteosarcoma

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

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

FISH: MDM2 non-amplified

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

Osteoid matrix: anastomosing trabeculae of predominantly woven bone

IHC: p53

FISH: MDM2 non-amplified

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