Lymphoid neoplasms: plasma cell dyscrasias

5 ASCP MLS practice questions on Lymphoid neoplasms: plasma cell dyscrasias, part of Hematology. The first 5 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

1. Question 1 · Easy

   Under the IMWG criteria, multiple myeloma needs a myeloma-defining event plus either a plasmacytoma or clonal bone marrow plasma cells of at least:

   1. A5%
   2. B20%
   3. C60%
   4. D10%

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   Answer: D · 10%

   The IMWG criteria (2014) require at least 10% clonal plasma cells in the marrow, or a biopsy-proven plasmacytoma, plus at least one myeloma-defining event. These events are the CRAB features (hypercalcemia, renal failure, anemia, bone lesions) or one of three biomarkers, one of which is 60% or more clonal plasma cells. A patient with 10% or more clonal plasma cells but no defining event has smoldering myeloma. Clonality is shown by kappa or lambda light-chain restriction.

   • A: Normal marrow usually has fewer than 5% plasma cells, and MGUS has fewer than 10%.
   • B: 20% is the blast threshold for acute myeloid leukemia, not a plasma cell criterion.
   • C: 60% or more clonal plasma cells is itself a myeloma-defining event, not the base threshold.

2. Question 2 · Medium

   On a peripheral blood film, rouleaux can be told apart from red cell agglutination because rouleaux:

   1. AAppears only in the thick part
   2. BDisperses when the blood is warmed
   3. CForms irregular grape-like clumps
   4. DForms linear coin-like stacks

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   Answer: D · Forms linear coin-like stacks

   Rouleaux are red cells stacked in chains like coins, caused by raised plasma proteins such as a paraprotein or fibrinogen that reduce the repulsion between cells. Agglutination is antibody-mediated and forms irregular clusters with no orderly stacking. Cold agglutinates break up on warming to 37 °C, while rouleaux do not; in a tube, rouleaux disperses with saline replacement. True rouleaux is seen in the thin area of the film, where red cells should lie singly.

   • A: Stacking only in the thick area is an artifact; true rouleaux persists in the thin area.
   • B: Dispersal on warming is typical of cold agglutinins, not rouleaux.
   • C: Irregular, grape-like clusters describe agglutination.

3. Question 3 · Hard

   A 71-year-old man has headaches, blurred vision and nosebleeds, with enlarged lymph nodes and spleen. Results: Hb 9.8 g/dL (98 g/L), WBC 6.1 × 10^3/µL (6.1 × 10^9/L), rouleaux on the film, normal calcium and creatinine, no lytic bone lesions, and an IgM kappa paraprotein of 3.8 g/dL (38 g/L). The marrow shows small lymphocytes, plasmacytoid lymphocytes and plasma cells. The most likely diagnosis is:

   1. ACold agglutinin disease
   2. BWaldenström macroglobulinemia
   3. CChronic lymphocytic leukemia
   4. DIgM multiple myeloma

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   Answer: B · Waldenström macroglobulinemia

   An IgM paraprotein with signs of hyperviscosity (headache, blurred vision, mucosal bleeding), lymphadenopathy, splenomegaly and a lymphoplasmacytic marrow infiltrate is the picture of Waldenström macroglobulinemia. The large IgM pentamer raises plasma viscosity far more than the same amount of IgG. Lytic bone lesions and hypercalcemia, typical of myeloma, are uncommon. Testing for MYD88 L265P supports the diagnosis, and plasmapheresis quickly relieves hyperviscosity.

   • A: Cold agglutinin disease shows agglutination with hemolysis, not rouleaux and hyperviscosity.
   • C: CLL would show an absolute lymphocytosis, and the WBC here is normal.
   • D: IgM myeloma is rare and shows a plasma cell infiltrate with lytic lesions, not lymphadenopathy with lymphoplasmacytic cells.

4. Question 4 · Medium

   Which flow cytometry profile is typical of the neoplastic plasma cells in multiple myeloma?

   1. ACD34+, CD117+, CD13+, CD33+
   2. BCD38 bright, CD138+, CD19-, CD56+
   3. CCD5+, CD19+, CD23+, CD20 dim
   4. DCD19+, CD20+, surface IgM+, CD38 dim

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   Answer: B · CD38 bright, CD138+, CD19-, CD56+

   Plasma cells express CD38 strongly and CD138 (syndecan-1), and they have lost B-cell markers such as CD20 and surface immunoglobulin. Neoplastic plasma cells usually lack CD19 and often express CD56 aberrantly, while normal plasma cells are usually CD19+ and CD56-. Clonality is shown by cytoplasmic kappa or lambda restriction. CD38 is also the target of daratumumab, which interferes with antibody screens in the blood bank.

   • A: CD34, CD117, CD13 and CD33 mark myeloid blasts.
   • C: CD5 and CD23 with dim CD20 is the classic CLL profile.
   • D: CD19, CD20 and surface IgM mark mature B cells, such as the lymphoplasmacytic cells of Waldenström.

5. Question 5 · Easy

   Which immunoglobulin forms the paraprotein in Waldenström macroglobulinemia?

   1. AIgG
   2. BIgA
   3. CIgD
   4. DIgM

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   Answer: D · IgM

   Waldenström macroglobulinemia is a lymphoplasmacytic lymphoma whose cells secrete monoclonal IgM. IgM is a large pentamer that stays mostly in the plasma, so even moderate amounts raise serum viscosity. Most patients carry the MYD88 L265P mutation, which helps separate it from other small B-cell lymphomas. Rouleaux and a raised ESR are common on routine testing.

   • A: IgG is the most common paraprotein in multiple myeloma, not in Waldenström.
   • B: IgA paraproteins occur in myeloma, in about one case in five.
   • C: IgD myeloma is rare and is not Waldenström macroglobulinemia.