MRI characteristics of chondroblastoma.

We report a retrospective study of MR imaging of 16 patients with histologically proven chondroblastoma, 12 at primary presentation and four clinically suspected recurrences. In all the primary cases MR imaging showed a lobulated low signal intensity (SI) rim. Low SI foci within the tumour were present in 11 out of the 12 cases and corresponded to calcification seen on radiographs or CT. Bone marrow oedema was also present in 11 out of 12 cases and an adjacent joint effusion in eight out of 12. The STIR sequence was of particular value, giving optimal delineation of marrow and soft tissue oedema. Of the suspected recurrences one showed peritumoral oedema and was subsequently proven histologically. Three showed no peritumoral oedema and subsequent histology was negative in these cases. The presence or absence of oedema may be a useful indicator of tumour activity although further study is required.