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Multiple Myeloma


KEY FACTS

Terminology

  • Multifocal malignant proliferation of monoclonal plasma cells within bone marrow

Imaging

  • Skeletal survey is initial diagnostic imaging evaluation

    • Diffuse osteopenia and multiple lytic lesions

  • NECT (bone algorithm)

    • Multifocal lytic lesions

    • Vertebral destruction and fractures

  • MR patterns

    • Normal

    • Focal marrow involvement

    • Diffuse marrow involvement

    • Variegated pattern (micronodular, “salt and pepper”)

  • Compression fractures with variable central canal narrowing

  • FDG PET

    • Identifies active multiple myeloma; useful in monitoring treatment response

  • FSE T2 with fat saturation, STIR, or T1WI C+ with fat suppression increase lesion conspicuity

Top Differential Diagnoses

  • Metastases

  • Leukemia/lymphoma

  • Osteoporosis

Clinical Issues

  • Bone pain: 75%

  • Marrow failure: Anemia, infection

  • Renal insufficiency/failure

  • Serum protein electrophoresis shows M protein (monoclonal immunoglobulin)

    • Immunofixation electrophoresis more sensitive for small amounts

  • Hypercalcemia

Sagittal STIR MR illustrates innumerable hyperintense foci in the cervical and thoracic vertebral bodies
and spinous processes
. Advanced imaging is recommended in those with normal radiographs and monoclonal gammopathy or a solitary plasmacytoma.

Sagittal T1WI MR demonstrates heterogeneous marrow signal due to fatty replacement by countless hypointense lesions in the vertebral bodies
and the spinous processes
. There is a benign vertebral hemangioma at T8
.

Sagittal T2WI MR (L) shows marrow heterogeneity with a hypointense L3 vertebral body lesion
, barely detectable on lateral MR (R)
. Radiographs allow identification of only those lesions with advanced destruction affecting at minimum 30% of trabecular bone.

Sagittal T1WI MR depicts fatty marrow replacement by several hypointense vertebral body lesions of varying sizes
. Posttreatment T1WI MR shows gradual replacement of infiltrates by red marrow, then by fat.

TERMINOLOGY

Abbreviations

  • Multiple myeloma (MM)

Definitions

  • Heterogeneous group of plasma cell neoplasms involving primarily bone marrow ± soft tissues

IMAGING

General Features

  • Best diagnostic clue

    • Multifocal, diffuse, or heterogeneous T1 hypointensity

  • Location

    • Axial skeleton (red marrow) > long bones

      • –

        Spine, skull (mandible), ribs, pelvis

    • 87% vertebral fractures between T6 and L4

  • Size

    • Variable

  • Morphology

    • Well-circumscribed, “punched-out” lesions on radiography

      • –

        May be expansile

Radiographic Findings

  • Radiography

    • Skeletal survey (SS) is initial diagnostic imaging evaluation

      • –

        Identifies those lesions with at least 30% destruction

    • Diffuse osteopenia: 85%

    • Multiple lytic lesions: 80%

      • –

        Approximately 1% of lesions sclerotic

    • Endosteal scalloping

    • Soft tissue mass adjacent to bone destruction

    • Plasmacytoma

      • –

        Solitary, large, expansile

      • –

        May be septated

    • Vertebral compression fractures

    • POEMS syndrome

      • –

        Enthesopathies of thoracolumbar posterior elements

      • –

        Lytic lesions with surrounding sclerosis

      • –

        Sclerotic lesions → may mimic prostate cancer

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