MRI features of extramedullary myeloma

The purpose of this study was to describe the MRI features of extramedullary myeloma and to evaluate the role of MRI in extramedullary myeloma.

The cases of 28 patients (15 men, 13 women; mean age, 57.53 years; range, 34-83 years) with extramedullary myeloma who underwent MRI at one institution from January 2004 through December 2012 were retrospectively identified through an electronic search of an institutional radiology database. Two radiologists reviewed images from 44 MRI examinations in consensus to document the morphologic, signal-intensity, and enhancement characteristics of extramedullary myeloma. Electronic medical records were reviewed to document the indication for MRI and subsequent management of extramedullary myeloma.

A total of 72 sites of extramedullary myeloma were noted, most commonly the paraspinal-epidural location (28/72, 39%). Two radiologic patterns were identified: lesions contiguous with bone (n = 44) and lesions noncontiguous with bone (n = 28). Lesions contiguous with bone were larger (p = 0.001; Student t test). Of 28 paraspinal-epidural lesions, 13 compressed the cord. Compared with skeletal muscle, most of the lesions were hypointense to isointense on T1-weighted images (67/72, 93.1%) and isointense to hyperintense on T2-weighted images (62/72, 86.1%). Lesions noncontiguous with bone were more often hypointense on T2-weighted images (8/28 vs 2/44; p = 0.006; Fisher exact test). Neurologic symptoms prompted MRI in most cases (n = 32/44). MRI was helpful in management by radiotherapy and surgery (19/28).

Extramedullary myeloma can be contiguous or noncontiguous with bone. Lesions contiguous with bone are larger, often occur in a paraspinal or epidural location, and can cause cord compression. Lesions noncontiguous with bone can be T2 hypointense. MRI helps in treatment planning.