Spinal osteoblastoma: CT and MR imaging with pathological correlation

Objectives. To illustrate the CT and MRI features of spinal osteoblastomas and correlate the imaging with histological findings. Design. In a retrospective review the CT and MRI features of spinal osteobl astomas with respect to mineralisation, signal intensity (SI), adjacent rea ctive changes, enhancement following gadolinium-DTPA (5 cases) and adjacent soft tissue masses were compared and correlated with the histological find ings including the degree of osteoid formation and matrix mineralisation, v ascularity and surrounding reactive changes in bone and soft tissue. Patients. Eleven patients (7 males and 4 females; age range 8-43 years, mea n age 19.5 years) with 12 osteoblastomas (1 patient suffered a recurrence) were studied. Results. All lesions showed classical features on CT with varying degrees o f matrix mineralisation, whereas MRI identified mineralisation in only eigh t of 12 cases. MRT showed low signal intensity of the lesion on both T1- an d T2-weighted sequences in several cases in the absence of heavy mineralisa tion. In these cases, histological examination revealed diffuse osteoid pro duction by the tumour. All patients given gadolinium showed enhancement wit hin the tumour on MRT. Reactive bone marrow changes were identified on MRI in 10 cases, and in five of these the changes were at multiple levels. An a djacent soft tissue mass was demonstrated in five cases, but extraosseous t umour was present histologically in only two of these. Conclusions. The MRT appearances of spinal osteoblastomas are varied and sh ow no characteristic features. MRI may also overestimate the extent of the lesion due to extensive reactive changes and adjacent soft tissue masses. C T should continue to be the investigation of choice for the characterisatio n and local staging of suspected spinal osteoblastomas.