Imaging of Multiple Myeloma: Present and Future

Abstract

Multiple myeloma (MM) is the second most common adult hematologic malignancy, and early intervention increases survival in asymptomatic high-risk patients. Imaging is crucial for the diagnosis and follow-up of MM, as the detection of bone and bone marrow lesions often dictates the decision to start treatment. Low-dose whole-body computed tomography (CT) is the modality of choice for the initial assessment, and dual-energy CT is a developing technique with the potential for detecting non-lytic marrow infiltration and evaluating the response to treatment. Magnetic resonance imaging (MRI) is more sensitive and specific than 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) for the detection of small focal lesions and diffuse marrow infiltration. However, FDG-PET/CT is recommended as the modality of choice for follow-up. Recently, diffusion-weighted MRI has become a new technique for the quantitative assessment of disease burden and therapy response. Although not widespread, we address current proposals for structured reporting to promote standardization and diminish variations. This review provides an up-to-date overview of MM imaging, indications, advantages, limitations, and recommended reporting of each technique. We also cover the main differential diagnosis and pitfalls and discuss the ongoing controversies and future directions, such as PET-MRI and artificial intelligence.

Keywords: computed tomography; imaging; magnetic resonance imaging; multiple myeloma; positron emission tomography.

Figure 1

Simplified algorithm for the diagnostic imaging management spectrum of monoclonal plasma cell disorders according to the IMWG consensus recommendations.MM: Multiple myeloma; SMM: smoldering multiple myeloma.

Figure 2

A 76-year-old man with IgG light chains in serum. Lytic lesion with soft tissue mass in the second right anterior costal arch with avid radiotracer uptake (arrows) in FDG-PET/CT in axial (top row) and coronal (bottom row) showing 18FDG uptake (A,D), CT (B,E), and fused images (C,F). Biopsy samples (G,H): the histological study revealed plasma cell proliferation leading to the diagnosis of MM.

Figure 3

A 56-year-old female with SMM presenting lumbar pain resistant to analgesia. PET/CT images in coronal (A–C) and sagittal (D–F) show diffuse MM involvement of the bone marrow with intense metabolic activity in the axial and peripheral skeleton, and sternal involvement (circles). Spine STIR sagittal sequence (G,H) showing increased bone marrow sternal signal (circle), concordant with FDG-PET/CT findings and burst fracture in T7 vertebral body with slight posterior wall retropulsion (arrows) poorly visualized in the FDG-PET/CT study because of its lower resolution and absence of metabolic activity.

Figure 4

Conventional CT multiplanar reconstructions. (A) Reconstruction in the sagittal plane for better assessment of the spine and the sternum. Multiple fractures in the thoracic and lumbar spine, some of them with vertebroplasty (arrows) with no visible lytic lesions. Horizontal fracture in the sternal body (arrowhead). (B–D) Reconstruction in different planes of the long bones for better assessment of cortical and the medullar cavity. Substitution of fatty bone marrow for areas of soft tissue density without endosteal scalloping in both femora and right humeri (arrows). The asymmetrical distribution favors tumoral infiltration over red marrow reconversion.

Figure 5

Normal bone (top row) vs. diffuse marrow infiltration with multiple osteolytic lesions (bottom row, arrows) in CT: (A,D) conventional CT, (B,E) grayscale VNCa image, and (C,F) color-coded VNCa image.

Figure 6

Sacral lytic lesion (yellow arrows) and diffuse marrow infiltration in the pelvis as the debut of MM with good correlation among conventional CT, DECT, MRI, and FDG-PET/CT. (A) Conventional CT. ROI average, 46 HU. (B) DECT VNCa grayscale (CaSupp index 25). ROI average, 3.2 HU. (C) DECT VNCa (CaSupp index 25) color-coded scale. (D) T1WI. (E) FST1WI after intravenous gadolinium administration. (F) FDG-PET/CT. Suvmax 29.5.

Figure 7

Diffuse MM bone marrow involvement of the axial and peripheral skeleton. No visible lytic lesions in WBLDCT (A). Diffuse bone marrow infiltration with high SI in b-900 MR-DWI ((B) and arrow in (C)) and pathological ADC values (878 μm²/s) in the vertebral body (circle in (D)). Malignant imaging features with diffuse bone marrow hypointensity in T1WI (E) and an SI drop of <20% between the in-phase (F) and opposed-phase MRI (G).

Figure 8

MM with associated plasmacytoma. T1WI (A,C) and STIR (B,D) show diffuse involvement of the bone marrow with soft tissue expansive mass (plasmacytoma) in the posterior elements of T11 (arrows) with severe stenosis of the vertebral canal (arrowhead in (D)). T1 (E) and STIR (F) show successful post-treatment changes with fat replacement (hyperintensity in T1) and >20% signal drop between in-phase (G) and opposed phase (H). There is an absence of FDG uptake (I) and a high SI on b-900 DWI (J), with an increase in ADC (K) (“T2-shine-through” effect), which demonstrates a lack of relapse.

Figure 9

CT and FDG-PET/CT correlation: three different scenarios. (A) A 68-year-old man with stage IIIB multiple myeloma with numerous 18FDG-avid lytic lesions in the axial skeleton. (B) A 71-year-old man with stage IIIB multiple myeloma. Lytic lesion in L3 without FDG uptake (arrow). (C) A 72-year-old man with stage IIB multiple myeloma. Multiple hypermetabolic foci in the sacrum and both ilia without correspondence in CT scan (arrows).

Figure 10

A 70-year-old woman with multifocal involvement of MM in the axial and peripheral skeleton. Multiple lesions with high SI in b = 900 DWI (A) and high SI in STIR (B). Follow-up FDG-PET/CT (C,D) shows successful post-treatment changes with no pathological FDG uptake.

Figure 11

A 68-year-old male who was admitted to the emergency department for subacute left infraclavicular pain that radiates to the left upper limb. (A) Chest X-ray revealed a mass in the left pulmonary apex (arrows). (B) Chest CT confirmed the presence of a mass in the left pulmonary apex (circle) with mediastinal extension, second left rib destruction, infiltration, and partial destruction of T2 vertebra with probable epidural soft tissue mass and soft tissue component in the adjacent extra thoracic musculature. The differential diagnosis was Pancoast tumor, metastasis of unknown neoplasm, lymphoma, and multiple myeloma/plasmacytoma. (C) Gadolinium-enhanced T1FSWI confirmed the solid nature of the lesion (arrow) and the presence of an epidural soft tissue mass causing cord compression (circle). (D) Histological (hematoxylin–eosin) and (E) immunochemical examinations revealed a clonal proliferation of plasma cells consistent with plasmacytoma. (F) Staging FDG-PET/CT evidenced hypermetabolism of the apical lesion with probable necrotic/hemorrhagic central component without distant skeletal uptakes or additional soft tissue masses. The patient was treated with decompressive surgery, RT, and chemotherapy (T1WI in (H)). (G) One-year follow-up PET/CT showed metabolic response with persistence of tumor.

Figure 12

Extraosseous spread of MM with arrows. (A) Right orbital mass, (B) retrothyroid conglomerate nodes, (C) pleural soft-tissue mass, (D) pericardial mass, (E) hypodense hepatic focal lesion, (F) soft-tissue confluent masses in perirenal fat and fascia, (G) pelvic soft-tissue mass, and (H) enlargement of right psoas secondary to tumoral infiltration.

Figure 13

Differential diagnosis in conventional CT. Multiple osseous lesions (arrows in (A)), some of them with mixed pattern and sclerotic rim (arrowhead in (B)) corresponding to lung cancer metastases, incompatible with untreated MM. Angioma in T12 vertebral body (arrows in (D,E)) with intralesional fat and intralesional thick trabeculae conforming to the typical “jail bar pattern” in sagittal reconstruction (D) and “polka dot pattern” in the axial plane (E). Degenerative disc disease in lumbar spine with multiple Schmörl nodules (arrowhead in (D)). We present a case of osteoporosis with multiple millimetric lytic lesions in coronal reconstruction of cervical spine (C), some of them with sclerotic rim (arrow in (C)) with a normal signal of the bone marrow in T1WI sequence (F) and no findings of hematologic cell dyscrasia in laboratory tests.

Figure 14

A 50-year-old patient with L5 vertebral body fracture secondary to diffuse tumor infiltration with the collapse of the upper plateau, posterior wall retropulsion, and anterior epidural soft tissue mass (arrows (A–F)), causing thecal sac indentation. MRI shows an L5 vertebral body malignant lesion with soft tissue expansion in the epidural anterior space in sagittal Dixon “only water” T2w (A) and contrast enhancement in sagittal gadolinium-enhanced T1FSWI (B) and axial T2w (C). The lack of FDH uptake in the L5 level can be observed in sagittal (D–F) and axial (H,I) FDG-PET/CT reconstructions, making it difficult to determine a pathologic fracture diagnosis. Histologic sample with hematoxylin–eosin staining diagnostic for plasmacytoma (G). The immunohistochemistry revealed monoclonal lambda light chains in plasma cells. The patient was treated with radiotherapy.