Bone lesions with soft-tissue mass: magnetic resonance imaging diagnosis of lymphomatous involvement of the bone marrow versus multiple myeloma and bone metastases.

Bone metastases from solid primary tumors, as well as multiple myeloma and secondary lymphoma may all present with bone lesions and associated soft-tissue masses on magnetic resonance images of the spine. In bone metastases and myeloma, the cortex of the affected bone is usually destroyed and a bulging contour is observed at the site of extraosseous spread. In cases of lymphomatous involvement of the bone marrow, however, we have observed that spread to the extraosseous soft-tissues occurs without alteration of the shape or contour of the affected bone. In order to assess whether this pattern of spread is indeed suggestive or even diagnostic of lymphoma of the bone marrow, we reviewed spinal bone marrow MR images of 66 patients, with bone metastases from solid primary tumors (33 patients), multiple myeloma (20 patients) and stage IV lymphoma with bone marrow involvement (13 patients), who had bone lesions and contiguous soft-tissue masses. If tumor was present on either side of the bony cortex but the contour of the affected bone was preserved, a "wrap-around" sign was diagnosed. A "wrap-around" sign was found in 12 of the 13 patients with lymphoma but in none of the patients with metastases or myeloma. On MR images of the bone marrow, the demonstration of tumor spread beyond the bony cortex without disruption of the outline of the diseased bone may favor the diagnosis of lymphoma more than that of metastases or multiple myeloma.