Imaging description

On radiography conventional chondrosarcomas typically show a lytic, lobulated, expansile lesion with scattered sclerotic areas which represent mineralized chondroid matrix (Figure 84.2). Characteristically a mineralized chondroid matrix reveals a punctate or popcorn pattern of calcifications. Higher-grade chondrosarcoma (grade 3) often contain less extensive areas of matrix mineralization. When these calcifications are tiny or faintly visualized, CT can show them better than radiography. The lesion appears to be slow growing and somewhat expansile causing some cortical thickening. With continued tumor growth endosteal scalloping develops and cortical disruption with invasion of the soft tissues can be detected. Murphey et al. stressed the importance of the extent of the endosteal scalloping (Figure 84.2). They believe that endosteal scalloping greater than two thirds the normal thickness of the long bone cortex is a strong evidence of chondrosarcoma rather than an enchondroma. They add that longitudinal endosteal scalloping in long bone lesions greater than two thirds of the lesion length is also more suggestive of chondrosarcoma than enchondroma.

MRI is the ideal method for demonstrating the extent of the marrow involvement as well as the soft tissue extension. The tumor reveals low to intermediate signal on T1-weighted sequence. The non-mineralized cartilaginous or myxoid component of the tumor shows high signal intensity on T2-weighted images. The mineralized cartilage shows low signal intensity on all MR pulse sequences. Conventional chondrosarcoma shows peripheral and septal enhancement following the IV injection of gadolinium (Figure 84.1).