Differentiation of Multiple Myeloma and Metastasis: Emphasis on Bone Marrow Invo l vement Pattern of Spine inSagittal MR Images

PURPOSE: To differentiate multiple myeloma and metastasis of the spine. MATERIALS AND METHODS: Retrospectiveanalysis of MR images of the patients with multifocal spinal involvement of multiple myeloma and metastasis wasdone. Analysis was done in viw points of bone marrow involvement pattern(focal, diffuse, and mixed), margin,number, size and uniformity of the focal lesions, involvement of pedicle and posterior element, and epidural andparavertebral mass formation. RESULTS: Multiple myeloma predominantly showed diffuse pattern (11/21, 52.4%) ofmarrow involvement, while metastasis showed mainly focal pattern (18/21, 85.7%). Margin of the focal lesions weredistinct in majority (8/10, 80%) of multiple myeloma and indistinct in majority (16/21, 76.2%) of metastasis. Sizeof the focal lesions were smaller in cases of multiple myeloma than those of metastasis, but number and standarddeviation of the size of the focal lesions did not show significant difference between the two diseases.Involvement of posterior element were more common in multiple myeloma, and epidural mass formation andparavertebral mass formation were more common in metastasis. CONCLUSION: The diffuse pattern of marrow involvementalone suggests multiple myeloma. When a focal or a mixed pattern is found, distinct margin and smaller focallesions are suggestive of multiple myeloma, and indistinct margin and larger focal lesions andepidural/paravertebral mass formation are suggestive of metastasis.