Imaging of chondrosarcoma

Chondrosarcoma is a malignant tumor of chondroid origin, the third most common bone tumor accounting for 25% of all bone malignancies. Types of chondrosarcomas include-Central and peripheral (based on location), clear cell, well differentiated, or mesenchymal (based on histology), and low, myxoid, high or dedifferentiated (based on grade). Also, enchondroma may dedifferentiate, and show areas of high-grade malignancy. Central chondrosarcoma is the most common type of chondrosarcoma (90%) and has a wide spectrum of imaging appearances. Distinguishing a chondroma from low-grade chondrosarcoma can be challenging. The presence of pain, atypical location, large size (> 5cm), suspicious calcification patterns, deep cortical scalloping, cortical penetration, periosteal reaction, cortical remodeling, inhomogeneous and variable MRI signals, soft tissue mass and high uptake on bone scan are features that indicate a low grade chondrosarcoma. Conventional clear-cell chondrosarcoma is a low grade variant. Mesenchymal chondrosarcoma is rare but has imaging features similar to the conventional type. Dedifferentiated chondrosarcoma is characterized by a bimorphic pattern of well-differentiated chondrogenic lesion and a high grade non-cartilagneous lesion. Juxtacortical chondrosarcoma is also rare, but is larger than chondroma, with striated calcification and no endosteal sclerosis. Secondary chondrosarcomas originate from benign cartilageneous lesions such as enchondroma or osteochondroma. Imaging plays an important role in the diagnosis and management of chondrosarcoma. Initial diagnosis is made by radiograph with CT and MRI useful in evaluating the extent of the disease.