MRI features of low-grade and high-grade chondrosarcoma in enchondromatosis

To identify magnetic resonance imaging (MRI) features which aid differentiation of low-grade chondral tumours (LGCT-enchondroma and grade 1 chondrosarcoma) from high-grade chondral tumours (HGCT) in patients with enchondromatosis. Approval from our local Research and Innovation Centre of The Institute of Orthopaedics was gained. Patients with enchondromatosis who had biopsy and/or resection of chondral lesions over a 13-year period were identified. The pre-biopsy MRI study was assessed by two experienced musculoskeletal radiologists for tumour origin (intramedullary or surface), cortical expansion, cortical destruction, bone marrow oedema, periosteal reaction, soft tissue mass and soft tissue oedema. MRI features were compared with the final histopathological diagnosis. The study group comprised 25 males and 16 females, with a mean age of 34.9 years (range 6-81 years). Fifty-nine lesions were assessed (12 patients had $>$ 1 tumour treated), including 43 LGCT and 16 HGCT. Significant MRI features suggesting malignant transformation to HGCT for both observers included bone oedema (p = $<$ 0.001 and 0.002), periosteal reaction (p = 0.01) and soft tissue oedema (p = 0.001 and 0.05). Cortical destruction and soft tissue mass were predictors of HGCT in major long bones, but no significant differentiating features were identified in the hands and feet. The presence of bone oedema, periosteal reaction and soft tissue oedema on MRI may indicate a high-grade malignant transformation of chondral tumours in patients with enchondromatosis.