RESUMO
Cartilage-cell-containing tumours of the pelvis are responsible for a quarter of all primary bone lesions in this site. Benign tumours are uncommon but when present have classical radiological appearances similar to those described elsewhere. Only the rarest, chondromyxoid fibroma, may cause difficulty in diagnosis. Seventy-three per cent of cartilage-cell tumours are malignant and are either chondrosarcoma or chondroblastic osteosarcoma. Chondrosarcoma occurs after the second decade of life, usually with a longer history, and may be categorised as either a secondary peripheral or primary central tumour, each having typical radiological features. Chrondroblastic osteosarcoma tends to occur in younger patients with a shorter clinical history and is almost exclusively situated adjacent to a sacroiliac joint, producing purely lytic, sclerotic or mixed patterns of bone destruction. Experience suggests that computed tomography is the single most valuable further examination, since the pelvis is a complex structure with confusing overlying soft-tissue artefacts. This technique may indicate both the route and choice of optimal biopsy site.