Imaging of primary multifocal osseous lymphoma.

OBJECTIVE: To review our experience with primary multifocal osseous lymphoma (PMOL), to characterize its imaging features, before and after treatment, and to correlate these features with clinical outcome.

DESIGN: Hospital charts and imaging studies in eight patients with PMOL were reviewed. These included bone radiographs, bone scans, CT and MRI. Number, distribution and appearance of lesions before treatment were evaluated; and post-treatment changes were assessed for evidence of healing or progression, correlated with clinical outcome.

RESULTS: A total of 63 lesions were identified by pre-treatment bone scan, 36 by MRI (including 10 not visible on bone scan) and 16 by radiographs. Twenty-one percent of lesions occurred about the knee, and 63% of patients had concomitant skull, distal femoral and proximal tibial lesions. The radiographic appearance ranged from lytic to sclerotic. Lesions were isointense to hematopoietic marrow on T2-weighted MR sequences. Only plain radiographic evidence of healing or progression correlated with clinical outcome.

CONCLUSION: Distribution of PMOL was best assessed by bone scan. However, MRI revealed larger areas of marrow involvement and detected lesions in the pelvis not seen on bone scan. Marrow involvement around the knee was common, and the combination of skull, distal femoral and proximal tibial lesions may suggest the diagnosis. Radiographs underestimate the extent of disease but were the best modality for assessment of treatment response.