| Conventional osteosarcoma | 10–25 (2nd peak > 60: Paget's, radiation) | metaphysis: distal femur > proximal tibia > proximal humerus | mixed lytic–sclerotic, cloud‑like osteoid matrix, wide zone, sunburst, Codman triangle, soft‑tissue mass with osteoid; skip lesions | commonest primary malignant bone tumour in young; lung metastases (may calcify, pneumothorax); retinoblastoma (RB1), Li–Fraumeni |
| Parosteal osteosarcoma | 20–40 | posterior distal femur (popliteal surface) | dense lobulated surface mass, string sign / cleavage plane (radiolucent line between tumour and cortex) | low grade, good prognosis; vs myositis ossificans (zonal pattern: mature periphery) |
| Periosteal osteosarcoma | 15–25 | tibial/femoral diaphysis | surface, spiculated, chondroid | intermediate grade |
| Telangiectatic osteosarcoma | young | metaphysis | lytic, fluid–fluid levels (mimics ABC) | — |
| Ewing sarcoma | 5–20 (commonest malignant bone tumour < 10) | diaphysis/metadiaphysis of femur, pelvis, ribs, flat bones | permeative, lamellated (onion‑skin) periosteal reaction, saucerisation (cortical erosion from outside), large soft‑tissue mass; may be sclerotic | t(11;22) EWSR1–FLI1, CD99; fever/ESR mimic infection; radiosensitive |
| Chondrosarcoma | > 40 | pelvis, proximal femur, shoulder girdle, ribs | lytic with rings and arcs/popcorn, deep endosteal scalloping (> 2/3 cortex), cortical thickening, periosteal reaction, soft‑tissue mass | secondary from enchondroma/osteochondroma; radio‑ and chemo‑resistant |
| Giant cell tumour | 20–40, physes closed | epimetaphyseal, eccentric, extends to subchondral bone; distal femur, proximal tibia, distal radius, sacrum | lytic, expansile, "soap‑bubble" trabeculation, narrow zone without sclerotic rim, cortical thinning ± breach | locally aggressive, recurrence; lung metastases ~2–5% ("benign metastasising"); denosumab |
| Chordoma | 40–60 | sacrococcygeal (commonest) > clivus (spheno‑occipital) > vertebral bodies (C2) | midline destructive lytic mass, calcification, large soft‑tissue component; very high T2 | notochordal remnant; brachyury |
| Adamantinoma | 20–40 | anterior tibial diaphysis | multiple cortical lucencies ("soap bubble"), sclerosis | osteofibrous dysplasia link |
| Primary lymphoma of bone | adults | diaphysis | permeative, minimal cortical destruction with a large soft‑tissue mass | — |
| Undifferentiated pleomorphic sarcoma (MFH) | > 50 | metaphysis | lytic, aggressive | after Paget's/infarct/radiation |