List the types of osteosarcoma (primary and secondary).

Primary
Intramedullary
Juxtacortical
Telangiectatic (may mimic an ABC) Intracortical (rare)

Secondary
Postradiation osteosarcoma
Osteosarcoma arising in Paget's disease
Dedifferentiated chondrosarcoma (chondrosarcoma dedifferentiates into a more primitive lesion with other cell types)