Classification of bone tumours
The World Health Organization's histologic classification of bone tumours separates the osteosarcomas into central (medullary) and surface (peripheral) tumours and recognizes a number of subtypes within each group (table 1).
The most common pathologic subtype is conventional high-grade central osteosarcoma. It accounts for 80-90% of all osteosarcomas and is characterized by areas of necrosis, atypical mitoses and malignant cartilage.
Its most frequent subtypes are osteoblastic, chondroblastic and fibroblastic osteosarcomas.
Table 1: Osteosarcoma subtypes within central and surface tumours
|a. Conventional high-grade central osteosarcoma|
b. Telangiectatic osteosarcoma
c. Intraosseous well-differentiated (low-grade) osteosarcoma
d. Small cell osteosarcoma
|a. Parosteal (juxtacortical) well-differentiated (low-grade) osteosarcoma|
b. Periosteal osteosarcoma - low- to intermediate-grade osteosarcoma
c. High-grade surface osteosarcoma