Chondrosarcoma

General characteristics

Chondrosarcoma is a malignant chondroid tumor. It is the fourth most common primary malignant bone tumor, after plasmocytoma, osteosarcoma, and Ewing's sarcoma.

Epidemiology

Its peak incidence is between 30 and 60 years of age. According to their intraosseous location, chondrosarcomas may be divided into central and peripheral lesions.

Location

Central chondrosarcomas occur both in tubular bones (e.g., femur, proximal humerus, proximal tibia) and in flat bones (e.g ., pelvis). Peripheral chondrosarcomas most commonly arise in flat bones (e.g., pelvis, ribs) and in the spine.

Morphology

Most chondrosarcomas (-75%) are primary and arise de novo, but the remaining 25% are secondary and develop from malignant transformation of a benign lesion, such as an enchondroma or an osteochondroma (rarely a chondroblastoma).

It is difficult to differentiate low-grade chondrosarcomas from benign chondroid lesions; however, the presence of pain in the absence of fracture and cortical destruction and the presence of a soft tissue mass are all signs suggestive of malignancy.

Imaging

On MR images, chondrosarcoma has a characteristic multilobular configuration. The lobules of hyaline cartilage have intermediate signal intensity, similar to that of muscle on T1-weighted images, and homogeneous high signal intensity on T2-weighted images. The fibrous septa have low signal intensity on both TI-weighted and T2-weighted images, but they enhance after Gd-DTPA administration. Calcifications are common in low-grade chondrosarcoma and are best seen by conventional radiography and CT. Endosteal scalloping is also best depicted with CT and plain radiography.