Incidental long bone cartilage lesions: is any further imaging workup needed?

To determine the rate of chondrosarcoma in incidentally discovered painless long bone cartilage lesions and to determine if any further imaging is needed.

A cartilage lesion was said to be an enchondroma when it had characteristic matrix mineralization and no aggressive features. Search of all imaging reports and tumor board files for keywords enchondroma, cartilage lesion, chondroid, and chondrosarcoma. Retrospective review of medical records and imaging studies from 4.5-year period. Data points collected included patient age, sex, lesion site, size, symptoms, type of imaging, imaging appearance, and length of follow-up. Only patients with no pain were included as enchondroma. Patients with final diagnosis of chondrosarcoma were included for comparison of all features.

Only 1/73 (1.4%) patients with an initial incidentally discovered painless lesion was later diagnosed, with new symptoms, as atypical cartilage tumor. Average age was 59.4 years. Bones involved were the femur (n = 33), humerus (n = 30), tibia (n = 7), fibula (n = 2), and ulna (n = 1). Average enchondroma size was 3.9 cm (range 1.4-11.5). Average follow-up was 47 months (range 2-196 months). Eleven long bone chondrosarcomas were identified. All chondrosarcoma patients had pain and aggressive imaging findings.

Our study reveals that the rate of chondrosarcoma in incidentally found painless chondroid lesions without aggressive features in long bones is low. Imaging follow-up may be needed only in the setting of new symptoms.