Multiple Myeloma



Multiple Myeloma


Todd M. Blodgett, MD

Alex Ryan, MD

Joanna Costello, MD





Key Facts


Terminology



  • Multiple myeloma (MM), monoclonal gammopathy of undetermined significance (MGUS)


  • Myeloma: Proliferation of clonal plasma cells and overproduction of monoclonal immunoglobulins


Imaging Findings



  • Increased activity in lytic lesion or extramedullary site on PET/CT


  • Multiple lytic or punched-out lesions are diagnostic of MM and are present in 75-90% of patients at diagnosis


  • Bone marrow and bone (97%)


  • PET/CT performs better than MR in the detection of focal lesions


  • Most studies have shown PET/CT reliable for bone lesions ≥ 1 cm using standard SUV cutoff of 2.5


  • PET provides accurate staging of untreated MM (solitary, multifocal)


  • Diffuse marrow uptake on PET usually indicates elevated plasma cell population


  • PET exceptionally useful in monitoring disease activity in patients with nonsecretory myeloma


Top Differential Diagnoses



  • Lytic Skeletal Metastases


  • Osteopenia, Osteoporosis


  • Other Bone + Soft Tissue Malignancy


  • Other Plasma Cell Neoplasms


Diagnostic Checklist



  • FDG PET/CT to stage and establish baseline for monitoring therapy (especially in nonsecretory myeloma)






Graphic shows the typical punched out appearance of bone with multiple lytic lesions image, representing the changes of multiple myeloma.






Axial CECT shows several lytic lesions image within a vertebral body and with the typical appearance of myeloma.


TERMINOLOGY


Abbreviations and Synonyms



  • Multiple myeloma (MM), monoclonal gammopathy of undetermined significance (MGUS)


Definitions



  • Malignancy of antibody-forming plasma cells in bone marrow



    • Overproduction of monoclonal immunoglobulins


    • Causes a wide variety of manifestations


IMAGING FINDINGS


General Features



  • Best diagnostic clue



    • Multiple lytic or punched out lesions are diagnostic of MM



      • Present in 75-90% of patients at diagnosis


    • PET: Increased activity in lytic lesion or extramedullary site



      • Not all lesions are hypermetabolic


  • Location



    • 97% of cases present in bone and bone marrow



      • Spine is the most common site of involvement of myeloma


      • Due to presence of red marrow in axial skeleton throughout life


    • Common extramedullary sites of occurrence: Paranasal sinuses, nasopharynx, tonsils



      • Less common: Lung, spleen, liver


    • Osteonecrosis of humeral and femoral heads reported in up to 10% of MM patients



      • Area of involvement is often asymptomatic


      • Risk factors include treatment with dexamethasone, male gender, younger age


  • Morphology



    • Increased complement of plasma cells in marrow and lytic bone lesions



      • Plasma cells > 10-15% of marrow cells


    • May present as solid mass (plasmacytoma) in bone or soft tissue


Imaging Recommendations



  • Best imaging tool



    • Prior to imaging, confirm disease via lab work and analysis of bone marrow aspiration



    • FDG PET useful for



      • Evaluation of disease activity


      • Detection of extraosseous disease involvement


      • Direction of local therapy (e.g., radiation)


      • Assessment of patients with nonsecretory myeloma


      • Evaluation of response to therapy


    • FDG PET/CT with contrast



      • Superior to MR in the detection of focal lesions


    • MR better for diagnosis of diffuse disease pattern



      • Limited window (spine and pelvis) reduces sensitivity


      • Generally reserved for evaluation of bone marrow in spine and pelvis


      • Improved ability to detect both focal and diffuse disease


  • Protocol advice



    • For detection of diffuse disease, obtain PET/CT from top of head to toes


    • For patients not affected by renal failure (which is common in MM), use oral and IV contrast-enhanced CT


    • Marrow stimulant drugs may mask underlying MM lesions


CT Findings



  • Plasma cell tumors in bone → ↑ osteoclasts and ↓ osteoblasts → “punched out” lesions in flat and long bones


  • NECT is indicated for evaluation of cortical destruction and intra-/extraosseous extent of tumor


  • Up to 30% demineralization required before lytic lesion may be detected


  • CT useful to guide percutaneous biopsies


  • Findings



    • Multiple well-defined, rounded, lytic, punched out lesions



      • Usual sites: Skull, spine, pelvis


    • Cortical and cancellous bone erosion


    • Endosteal scalloping (may be subtle)


    • Diffuse osteopenia, osteoporosis, osteolysis, with accentuated trabecular pattern


    • Minimal periosteal new bone formation


    • Lesions often become sclerotic after therapy


  • Spine



    • Vertebral collapse



      • Large endplate depressions


      • Sparing of posterior elements


    • Paraspinal/epidural soft tissue mass adjacent to bone destruction


  • Plasmacytoma



    • Solitary expansile lesions present in 10% of cases


    • May appear as bubbly expansion of single bone


    • Occasionally associated with soft tissue mass


    • Represents early stage of melanoma (progresses to multiple lesions)


    • Presents most commonly in ribs, pelvis, long bones


    • Discovery of second myeloma lesion upstages patient’s disease from I to III


  • Benign fracture suggested by



    • Retropulsed posterior fragment


    • Cortical fragments without destruction


    • Identifiable fragment lines within cancellous bone


    • Intravertebral vacuum phenomenon


    • Thin diffuse paraspinal soft tissue mass


Nuclear Medicine Findings



  • General



    • False positives seen with infection, inflammation, post-surgical changes, and hemangioma


  • Initial diagnosis



    • Most studies have shown PET/CT reliable for bone lesions of at least 1 cm using standard SUV cutoff of 2.5



      • Any lesions smaller than 5 mm with uptake should be considered positive, regardless of SUV


    • Stable MGUS may be diagnosed based on negative whole body PET in patients with monoclonal gammopathy


    • PET/CT can be useful for diagnosing infection, even with severe neutropenia/lymphopenia



      • Nearly 10% of newly diagnosed patients die within 60 days of complications due to infection or renal failure



      • Silent infections are also detected and should be considered in the differential diagnosis of FDG-avid foci


  • Staging

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Sep 22, 2016 | Posted by in MAGNETIC RESONANCE IMAGING | Comments Off on Multiple Myeloma

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