Pathology: osteosarcoma, conventional

Osteosarcoma, conventional, osteoblastic

• Sheets and trabeculae of epithelioid-polygonal cells

• Amphophilic cytoplasm

• Round-ovoid nuclei with prominent nucleoli and moderate pleomorphism; mitotic activity 

• Sheets of osteoid with variable mineralization

Osteosarcoma, conventional, chondroblastic

• Sheets of polygonal cells

• Amphophilic cytoplasm

• Round-ovoid nuclei with marked pleomorphism; mitotic activity

• Prominent hyaline cartilage matrix; rare seams-sheets of osteoid with variable mineralization; focal osteoblastic differentiation

Osteosarcoma, conventional, osteoblastic

• Sheets of polygonal cells

• Amphophilic cytoplasm

• Round-ovoid nuclei with marked pleomorphism; brisk mitotic activity

• Delicate seams and sheets of osteoid with variable mineralization 

Osteosarcoma, conventional, chondroblastic

• Sheets of polygonal cells

• Eosinophilic cytoplasm

• Round-ovoid nuclei with marked pleomorphism; brisk mitotic activity

• Prominent hyaline cartilage matrix; seams-sheets of osteoid with variable mineralization; focal osteoblastic differentiation

Osteosarcoma, conventional, chondroblastic

• Sheets of polygonal cells

• Eosinophilic cytoplasm

• Round-ovoid nuclei with marked pleomorphism; brisk mitotic activity

• Prominent hyaline cartilage matrix; seams-sheets of osteoid with variable mineralization; focal osteoblastic differentiation

Osteosarcoma, conventional, fibroblastic

• Spindle-polygonal cells with storiform-fascicular pattern

• Eosinophilic cytoplasm

• Ovoid nuclei with occasional multinucleation and marked pleomorphism; conspicuous mitotic activity

• Secondary aneurysmal cyst formation; osteoid* with mineralization

* Osteoid may be very focal necessitating extensive sampling for definitive classification

Osteosarcoma, conventional, epithelioid

• Sheets of epithelioid cells

• Amphophilic cytoplasm

• Round-ovoid nuclei with macronucleoli and moderate pleomorphism; mitotic activity

• Delicate seams of osteoid with variable mineralization; focal chondroid differentiation; ectatic and branching vasculature

• IHC: SATB2

Osteosarcoma, conventional, giant cell-rich

• Sheets of polygonal cells

• Amphophilic cytoplasm

• Round-ovoid nuclei with small nucleoli and moderate pleomorphism; mitotic activity

• Prominent osteoclast-type giant cells; seams and sheets of osteoid with mineralization

Osteosarcoma, conventional, giant cell-rich

• Sheets of epithelioid cells

• Amphophilic cytoplasm

• Round-ovoid nuclei with prominent nucleoli and moderate pleomorphism; mitotic activity

• Prominent osteoclast-type giant cells; seams and sheets of osteoid with minimal mineralization