Chondrosarcoma of the para-acetabulum: correlation of imaging features with histopathological grade

To evaluate the computed tomography (CT) and magnetic resonance (MR) imaging features of para-acetabular chondrosarcoma (CS) and assess the difference between low-grade CS (LGCS) and high-grade CS (HGCS).

Thirty-one patients with histopathologically confirmed central para-acetabular CSs (6 LGCS and 25 HGCS) were retrospectively reviewed. Image features were evaluated for the following: cortical destruction, tumor border and pattern, calcification mode, soft-tissue mass, density/signal intensity, peritumoral edema, acetabular (cartilage) destruction, diffuse signal changes in acetabulum, mass inside hip joint, femoral head involvement, enhancement manifestations and the maximum length of the tumor. These image features between LGCS and HGCS were also assessed.

The most common CT and/or MR findings included cortical destruction, punctate, ring-and-arc and linear calcification, soft-tissue mass, lobulated border, high signal intensity with low signal septa on T2-weighted image, peritumoral edema, hip joint infiltration, peripheral and septal enhancement on post-enhanced MR image. Statistical analysis showed that the image features, such as cortical destruction, soft-tissue mass, hip joint infiltration and tumor size were significantly different between LGCS and HGCS (p < 0.05).

The characteristic radiological features of para-acetabular CSs are osteolytic lesions with cortical destruction, soft-tissue mass, lobulated border, calcification, and high signal intensity with low signal septa on T2-weighted MR image, peripheral and septal enhancement on post-enhanced MR image. Cortical destruction, soft-tissue mass, hip joint infiltration and tumor size can differentiate HGCS from LGCS.