Multiple myeloma vs Plasmacytoma and bone metastasis
How to tell Multiple myeloma and Plasmacytoma and bone metastasis apart when a board question makes them look alike.
Myeloma is systemic plasma-cell CRAB disease; plasmacytoma is solitary plasma-cell mass; metastasis is bone involvement from another primary cancer.
Side by side
Multiple myeloma causes clonal plasma-cell disease with CRAB findings, punched-out lytic lesions, M spike, light chains, rouleaux, and recurrent infections.
Plasmacytoma is a solitary plasma-cell mass; bone metastasis causes multifocal bone lesions from non-plasma-cell malignancy, often prostate, breast, lung, kidney, or thyroid.
Malignant plasma cells secrete monoclonal immunoglobulin and activate osteoclasts while suppressing normal humoral immunity.
Plasmacytoma remains localized; metastases seed bone from distant primary cancers and may be lytic, blastic, or mixed.
Bone marrow plasma cells, M protein, renal injury, hypercalcemia, anemia, and lytic skull lesions support multiple myeloma.
Single lesion without systemic marrow disease supports plasmacytoma; known solid tumor and lesion pattern support metastasis.
The trap
All can make lytic bone pain, so monoclonal protein, marrow burden, CRAB features, and primary tumor history separate them.
The repair move
For lytic bone lesions, decide plasma-cell systemic disease, solitary plasma-cell mass, or metastasis from another primary.
Try a free question
CoreA 68-year-old man has 5 months of fatigue, back pain, and recurrent infections. Labs: hemoglobin 8.2 g/dL, calcium 11.8 mg/dL, creatinine 2.4 mg/dL. Skeletal survey shows multiple punched-out lytic lesions in the skull, spine, and pelvis. SPEP shows a monoclonal IgG kappa spike. Bone marrow biopsy shows 32% clonal plasma cells. Which diagnosis is most likely?
Show answer and explanation
Answer: A. Multiple myeloma. Multiple myeloma is diagnosed by clonal bone marrow plasma cells >=10% plus CRAB end-organ damage (hypercalcemia, renal failure, anemia, lytic bone lesions); monoclonal protein on SPEP is characteristic; treatment combines proteasome inhibitors, immunomodulators, and stem cell transplant.
Why the other choices are tempting
- B. Solitary plasmacytoma is a SINGLE plasma-cell mass without systemic CRAB or marrow involvement.
- C. MGUS has M-protein <3 g/dL, marrow plasma cells <10%, and NO end-organ damage.
- D. Bone metastasis from prostate cancer typically produces OSTEOBLASTIC (sclerotic) lesions, not lytic.
- E. Lymphoma involving bone shows B-cell lineage on histology, not plasma cell clones.
Flashcards
Tap a card to flip it.
What does CRAB stand for in myeloma?
CRAB means hyperCalcemia, Renal dysfunction, Anemia, and Bone lesions.
What finding supports plasmacytoma?
A solitary plasma-cell mass without systemic myeloma features supports plasmacytoma.
Quick answers
What is the fastest way to tell Multiple myeloma from Plasmacytoma and bone metastasis?
Myeloma is systemic plasma-cell CRAB disease; plasmacytoma is solitary plasma-cell mass; metastasis is bone involvement from another primary cancer.
What is the key clue for Multiple myeloma?
Multiple myeloma causes clonal plasma-cell disease with CRAB findings, punched-out lytic lesions, M spike, light chains, rouleaux, and recurrent infections.
What is the key clue for Plasmacytoma and bone metastasis?
Plasmacytoma is a solitary plasma-cell mass; bone metastasis causes multifocal bone lesions from non-plasma-cell malignancy, often prostate, breast, lung, kidney, or thyroid.
What is the common trap with Multiple myeloma vs Plasmacytoma and bone metastasis?
All can make lytic bone pain, so monoclonal protein, marrow burden, CRAB features, and primary tumor history separate them.