Multiple Myeloma (MM)

Diagnosis
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  • Multiple Myeloma (MM) is diffuse or multifocal involvement of hematologic tumors of plasma cell origin
  • It most commonly occurs in males in their 60’s
  • A single metastatic lesion of plasma cell origin is termed a plasmacytoma
  • Predilection sites of MM are the ribs, sternum, scapula, skull, spine, pelvis, humerus, and femur
  • Complications of MM include bone pain/fractures, frequent infections, reduced renal function, and anemia
  • Bone scintigraphy is not useful to detect MM because the disease process inhibits osteoblastic activity
  • Lytic bone lesions from MM can be difficult to see on radiographs or even CT scans
  • MRI is the most sensitive and specific imaging method for the detection of bone marrow infiltration before mineralized bone has been destroyed
  • PET/CT and whole-body MRI combined is more effective than either modality alone in detecting MM
  • Patterns of bone marrow infiltration include normal appearing marrow, focal infiltration, diffuse disease, heterogeneous “salt-and-pepper” involvement, or combined focal and diffuse infiltration
  • MRI typically shows lesions that are hypointense on T1-weighted images, hypointense to isointense on T2, and hyperintense on STIR
  • The benefit of contrast use must be weighed against the risk of developing nephrogenic systemic fibrosis in patients with MM-associated renal failure
  • High signal within affected ribs on T2-weighted images with fat suppression is called the “white ribs sign”
  • Decreased lesion size and a high signal peripheral halo of fatty marrow (aka “fatty halo sign”) on T1  indicates treatment response
  • The differential diagnosis of MM on MRI includes leukemia, lymphoma, and metastases
  • Bone lesions often include cortical breakthrough and extension into the soft tissues; epidural extension can result in emergent cord compression
  1. Leucovet FE, Vande Berg BC, Malghem J, et al.  Magnetic resonance and computed tomography imaging in multiple myeloma.  Semin Musculoskelet Radiol 2001; 5(1):43-55
  2. Hanrahan CJ, Christensen CR, Crim JR. Current concepts in the evaluation of multiple myeloma with MR imaging and FDG PET/CT.  RadioGraphics 2010; 30(1):127–142