Dedifferentiated chondrosarcoma of the appendicular skeleton: MRI-pathological correlation.

Objective: To correlate the T2-weighted and STIR MRI appearances of dedifferentiated appendicular chondrosarcoma with gross and microscopic pathology.

Design And Patients: Nine patients with a histologically confirmed diagnosis of dedifferentiated appendicular chondrosarcoma were identified from the Bone Tumour Registry. All patients underwent MRI, including T2-weighted and/or STIR sequences in at least one plane, prior to limb salvage surgery. Areas of reduced signal intensity (SI) compared with hyperintense chondral tumour on the T2-weighted or STIR images were correlated with the resection specimen, to determine the relationship of such out areas of reduced SI with regions of dedifferentiation.

Results And Conclusions: Patients presented over a period of 7 years. There were five men and four women with mean age 68.2 years and age range 51-78 years. Tumours arose in the femur (6 cases), humerus (2 cases) and tibia (1 case). Three MRI patterns were identified: (1) type 1, a lesion with two distinct signal characteristics-hyperintense chondral and reduced SI dedifferentiated tumour (n=6); type 2, mainly reduced SI lesion-dedifferentiated tumour, with areas of signal void corresponding to matrix calcification (n=2); type 3, a heterogeneous lesion with no radiological evidence of underlying chondral tumour (n=1). T2-weighted or STIR MR sequences can identify areas of dedifferentiation, which should be the preferential site of pre-operative biopsy.