Bizarre parosteal osteochondromatous proliferation

Nodular; disorganized arrangement of bone, cartilage, and spindle cells

Bone trabeculae are irregular and anastomosing with prominent osteoblastic rimming

Cartilage is hypercellular with variable mineralization (so-called "blue bone"); polygonal cells with eosinophilic cytoplasm; round-ovoid nuclei with hyperchromasia and mild pleomorphism, and inconspicuous mitotic activity

Fibroblasts are spindle-stellate and set within collagenous-hyaline stroma; eosinophilic cytoplasm with delicate tapering processes; monomorphic ovoid nuclei with inconspicuous mitotic activity

Nodular; disorganized arrangement of bone, cartilage, and spindle cells

Peripheral bone trabeculae with osteoblastic rimming

Cartilage is hypercellular with abundant mineralization (so-called "blue bone"); polygonal cells with eosinophilic cytoplasm; round-ovoid nuclei with hyperchromasia and mild pleomorphism, and inconspicuous mitotic activity

Fibroblasts are spindle-stellate and set within collagenous-hyaline stroma; eosinophilic cytoplasm with delicate tapering processes; monomorphic ovoid nuclei with inconspicuous mitotic activity

Nodular; disorganized arrangement of bone, cartilage, and spindle cells

Bone trabeculae are irregular and anastomosing with prominent osteoblastic rimming

Cartilage is hypocellular with minimal mineralization; polygonal cells with eosinophilic cytoplasm; monomorphic hyperchromatic round-ovoid nuclei

Fibroblasts are spindle-stellate and set within collagenous stroma; eosinophilic cytoplasm with delicate tapering processes; monomorphic ovoid nuclei with inconspicuous mitotic activity