MRI-histopathological correlation in paediatric conventional central chondrosarcoma: a report of 17 cases.

OBJECTIVE To describe the MRI features of paediatric conventional central chondrosarcoma (CC-CS) and correlate with histological grade. MATERIALS AND METHODS A retrospective review of children/adolescents with histologically confirmed CC-CS. Data collected included age, sex, skeletal location, and histology from needle biopsy or resection, which was classified as atypical cartilaginous tumours/grade 1 CS (ACT/Gd 1 CS), high-grade chondrosarcoma (HGCS), and dedifferentiated chondrosarcoma (DD-CS). MRI studies were reviewed independently by 2 radiologists blinded to the histology grade, who graded the tumours as ACT/Gd 1 CS, HGCS, and DD-CS based on MRI features. RESULTS The study included 7 males and 10 females with mean age 13.9 years (range 6-18 years). Tumours were located in the femur (n = 6), humerus (n = 3), tibia, ilium, scapula, and ulna (n = 1 each), and the small bones of the hands or feet (n = 4). Final histology grade was ACT/Gd 1 CS in 15 cases and HGCS in 2 (both grade 1 CS with focal transition to grade 2), 15 based on surgical specimens, 1 based on open biopsy, and 1 on needle biopsy alone. Predicted MRI grade for the 2 readers was ACT/Gd 1 CS in 11 cases each and HGCS in 6 cases each, indicating a mismatch between predicted MRI grade and histological grade in 8 (47%) cases (4 cases with one reader mismatch and 4 cases with both). CONCLUSIONS MRI findings in paediatric CC-CS may be misleading, showing features suggestive of HGCS 7 of 17 (41.2%) of cases. This should be taken into consideration when planning surgical treatment.