Multiple Myeloma / Plasmacytoma¶

Definition¶

Multiple myeloma is a malignant proliferation of plasma cells that produces widespread skeletal destruction. The spine is one of the most commonly affected sites. A solitary plasmacytoma is a single focus of neoplastic plasma cells without evidence of systemic myeloma.

Imaging Findings¶

MRI¶

• Diffuse marrow infiltration — Diffuse low T1 signal throughout the vertebral bodies, replacing normal fatty marrow. High STIR signal. This is the most common pattern.
• Focal lesions — Multiple discrete round lesions scattered throughout the vertebral bodies (T1 low, T2/STIR high, enhancing)
• Variegated (salt-and-pepper) — Mixed areas of normal and abnormal marrow
• Normal-appearing marrow — Early myeloma may have a normal MRI appearance
• Compression fractures — Common, often multiple levels
• No significant osteoblastic response — Distinguishes myeloma from most metastatic disease on bone scan

CT¶

• Multiple well-defined "punched out" lytic lesions without sclerotic margins
• Diffuse osteopenia
• Endosteal scalloping
• No periosteal reaction (typically)
• Pathological compression fractures

Radiography¶

• Diffuse osteopenia ("washed out" vertebral bodies)
• Punched-out lytic lesions
• Compression fractures

Nuclear Medicine¶

• Bone scan is characteristically NEGATIVE — Myeloma is a purely lytic process that does not stimulate osteoblastic activity, so there is minimal radiotracer uptake. This is a major pitfall.
• PET/CT — Sensitive for myeloma; FDG-avid lesions

Solitary Plasmacytoma¶

A solitary plasmacytoma appears as a single expansile lytic lesion, most commonly in the vertebral body. It may show cortical expansion, soft tissue mass, and epidural extension. Approximately 50–70% of solitary plasmacytomas eventually progress to multiple myeloma.

Key Points¶

• Multiple myeloma produces diffuse marrow infiltration and/or multiple focal lytic lesions
• Bone scan is characteristically negative — a major diagnostic pitfall
• PET/CT and whole-body MRI are the preferred imaging modalities
• Low T1 marrow signal throughout the spine is the most common MRI pattern
• Solitary plasmacytoma may progress to systemic myeloma in 50–70% of cases
• Punched-out lytic lesions without sclerotic margins are characteristic on CT

References¶

1. Rajkumar SV, Dimopoulos MA, Palumbo A, et al. International Myeloma Working Group updated criteria for the diagnosis of multiple myeloma. Lancet Oncol. 2014;15(12):e538–e548. doi:10.1016/S1470-2045(14)70442-5. PMID: 25439696.
2. Wu F, Bernard S, Fayad LM, et al. Updates and Ongoing Challenges in Imaging of Multiple Myeloma: AJR Expert Panel Narrative Review. AJR Am J Roentgenol. 2021;217(4):775–785. doi:10.2214/AJR.21.25878. PMID: 33978464.
3. Dutoit JC, Verstraete KL. MRI in multiple myeloma: a pictorial review of diagnostic and post-treatment findings. Insights Imaging. 2016;7(4):553–569. doi:10.1007/s13244-016-0492-7. PMID: 27164915.
4. Hameed M, Sandhu A, Soneji N, et al. Pictorial review of whole body MRI in myeloma: emphasis on diffusion-weighted imaging. Br J Radiol. 2020;93(1115):20200312. doi:10.1259/bjr.20200312.
5. Albagoush SA, Shumway C, Azevedo AM. Multiple Myeloma. In: StatPearls. Treasure Island (FL): StatPearls Publishing; updated 2023 Jan 30. Available from: https://www.ncbi.nlm.nih.gov/books/NBK534764/.
6. Gaillard F, et al. Solitary bone plasmacytoma. Radiopaedia.org. Available from: https://radiopaedia.org/articles/solitary-bone-plasmacytoma-1.

Related Articles¶

• Vertebral Body Metastases
• Blastic vs Lytic Metastases
• Lymphoma of the Spine