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PubMed This is a summary of 16 peer-reviewed journal articles Updated
Hematology

The Biology and Genetics of Your Diagnosis

At a Glance

Waldenström macroglobulinemia is diagnosed by finding lymphoplasmacytic lymphoma in the bone marrow together with a monoclonal IgM protein in the blood. MYD88 and CXCR4 mutation results add important information about disease biology and treatment response.

The biology of Waldenström macroglobulinemia (WM) is a unique combination of two key findings. To have a definitive diagnosis, your medical team must find two specific things: a certain type of lymphoma in your bone marrow and a specific protein in your blood [1]. Understanding how these two elements interact—and the genetic “on-switches” that drive them—is key to managing the disease.

The Two-Part Diagnostic Assessment

A diagnosis of WM is not made based on a blood test alone. It requires an integrated look at your cells and your chemistry by a hematopathologist:

  1. The Tissue: A bone marrow biopsy must show lymphoplasmacytic lymphoma (LPL) [1]. These are abnormal cells that look like a cross between a mature B cell and a plasma cell [2]. Guidelines generally look for at least 10% of your bone marrow to be “infiltrated” by these cells, though this is context-dependent and heavily influenced by symptoms [1].
  2. The Protein: You must have a monoclonal IgM protein (often called a “paraprotein” or “M-spike”) in your blood [3].

The Genetic Drivers: MYD88 and CXCR4

In recent years, researchers have discovered that specific genetic mutations act as the “engine” for WM. Testing for these is now a standard part of a thorough evaluation. (Note: these are somatic mutations acquired during your lifetime, not inherited family mutations).

The MYD88 Mutation (The “On-Switch”)

More than 90% of people with WM have a specific mutation called MYD88 L265P [4][5].

  • What it does: This mutation causes the MYD88 protein to get stuck in the “on” position. It sends constant growth signals through pathways called NF-κB and BTK (Bruton’s Tyrosine Kinase) [2][6].
  • Why it matters: Because this mutation drives the disease through the BTK pathway, it makes many WM cases highly sensitive to a class of drugs called BTK inhibitors [6].

The CXCR4 Mutation (The “Homing Signal”)

About 30% to 40% of WM patients also have a mutation in the CXCR4 gene [4].

  • What it does: CXCR4 acts like a GPS signal that helps lymphoma cells “home” into the bone marrow and stay there, surviving longer than they should [7][8].
  • Why it matters: Patients with a CXCR4 mutation may have a higher “burden” of disease, such as more lymphoma cells in the marrow and higher IgM levels [9]. It also affects treatment: these cases often respond more slowly to certain drugs, and the “depth” of the response might not be as great as in those without the mutation [10][11].

Your Pathology Report Checklist

Your pathology report is the “map” of your disease. Because WM can look similar to other blood cancers (like marginal zone lymphoma or IgM myeloma), the hematopathologist integrates all findings to ensure the diagnosis is correct [12][5].

Check your report for these supportive elements (note that not all are strictly required for diagnosis):

  • Bone Marrow Infiltration Percentage: How much of the marrow is taken up by lymphoma cells (often >10%) [1].
  • Cell Pattern: Terms like “interstitial” or “paratrabecular” describe how the cells are spread out [13].
  • Morphology: Look for mentions of Dutcher bodies (clumps of IgM inside a cell) or an increase in mast cells (a type of immune cell often found near WM cells) [12].
  • Immunophenotype (Flow Cytometry): Confirms the cells have the right “ID tags” (usually positive for CD19 and CD20, but typically negative for CD5 and CD10, though expression can vary) [14].
  • Mutation Status: Explicit results for MYD88 and CXCR4 [5]. A negative MYD88 result does not completely rule out WM.
  • Cytogenetics: Mentions of chromosomal changes, such as deletion 6q, which is common in WM [6].

If your report is missing these details, or if it says “MYD88 wild-type” (meaning no mutation was found), it is particularly important to discuss these findings with a specialist, as wild-type WM can sometimes behave differently and may require a different diagnostic approach [15][16].

Common questions in this guide

What findings are needed to diagnose Waldenström macroglobulinemia?
Diagnosis generally requires both lymphoplasmacytic lymphoma in the bone marrow and a monoclonal IgM protein in the blood. A blood test alone is not enough, and the marrow findings must be interpreted in context by a hematopathologist.
What does a MYD88 L265P result mean in WM?
MYD88 L265P is a mutation acquired during life and is found in more than 90% of people with WM. It keeps growth signals active, including the BTK pathway, which helps explain why many WM cases respond to BTK inhibitors.
How can a CXCR4 mutation affect my WM?
A CXCR4 mutation can help lymphoma cells remain in the bone marrow and is associated with a greater amount of disease in some patients. It may also mean a slower or less deep response to certain medicines, so the result can help inform treatment planning.
What should I look for in a WM pathology report?
It may report the percentage of bone marrow involved, how cells are arranged, cell features such as Dutcher bodies or nearby mast cells, and their marker pattern on flow cytometry. It may also list MYD88 and CXCR4 results and chromosome changes such as deletion 6q. Not every supportive feature is required, so review the report with a WM specialist.
Does a negative MYD88 test rule out Waldenström macroglobulinemia?
No. A negative or wild-type MYD88 result does not completely rule out WM, but it can make the diagnosis more challenging and may prompt careful review of the marrow, blood findings, and other possible diagnoses by a specialist.

Questions For You

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Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.What percentage of my bone marrow is involved with lymphoma cells?
  2. 2.Did my pathology report confirm supportive features like 'Dutcher bodies' or a specific cell marker pattern?
  3. 3.Am I positive for the MYD88 mutation, and what was the sensitivity of the test used?
  4. 4.Do I have a CXCR4 mutation, and if so, how does that affect my treatment choices?
  5. 5.How does my mutation status affect your recommendation for my specific treatment plan?
  6. 6.Were any other chromosomal changes, like a 6q deletion, found in my marrow sample?

References

References (16)
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    Waldenström Macroglobulinemia: 2025 Update on Diagnosis, Risk Stratification, and Management.

    Gertz MA

    American journal of hematology 2025; (100(6)):1061-1073 doi:10.1002/ajh.27666.

    PMID: 40095219
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    MYD88 gene and protein: molecular architecture, signalling mechanisms and clinical implications in lymphoid malignancies.

    Banerjee Nair S, Hyun TS, Naresh KN

    Journal of clinical pathology 2026; (79(6)):363-369 doi:10.1136/jcp-2026-210690.

    PMID: 41922162
  3. 3

    Report of consensus Panel 4 from the 11th International Workshop on Waldenstrom's macroglobulinemia on diagnostic and response criteria.

    Treon SP, Tedeschi A, San-Miguel J, et al.

    Seminars in hematology 2023; (60(2)):97-106 doi:10.1053/j.seminhematol.2023.03.009.

    PMID: 37173155
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    SOHO State of the Art Updates and Next Questions | The Optimal Management of Waldenström Macroglobulinemia.

    Guijosa A, Heras AL, Sarosiek S, Castillo JJ

    Clinical lymphoma, myeloma & leukemia 2025; doi:10.1016/j.clml.2025.06.017.

    PMID: 40681432
  5. 5

    New developments in the diagnosis and characterization of Waldenström's macroglobulinemia.

    García-Sanz R, Hunter ZR, Poulain S, et al.

    Expert review of hematology 2023; (16(11)):835-847 doi:10.1080/17474086.2023.2270779.

    PMID: 37905549
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    Genomics, Signaling, and Treatment of Waldenström Macroglobulinemia.

    Hunter ZR, Yang G, Xu L, et al.

    Journal of clinical oncology : official journal of the American Society of Clinical Oncology 2017; (35(9)):994-1001 doi:10.1200/JCO.2016.71.0814.

    PMID: 28294689
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    Genomic Landscape of CXCR4 Mutations in Waldenström Macroglobulinemia.

    Poulain S, Roumier C, Venet-Caillault A, et al.

    Clinical cancer research : an official journal of the American Association for Cancer Research 2016; (22(6)):1480-8 doi:10.1158/1078-0432.CCR-15-0646.

    PMID: 26490317
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    Hematologic disorder-associated Cxcr4 gain-of-function mutation leads to uncontrolled extrafollicular immune response.

    Alouche N, Bonaud A, Rondeau V, et al.

    Blood 2021; (137(22)):3050-3063 doi:10.1182/blood.2020007450.

    PMID: 33512437
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    CXCR4 mutations affect presentation and outcomes in patients with Waldenström macroglobulinemia: A systematic review.

    Castillo JJ, Moreno DF, Arbelaez MI, et al.

    Expert review of hematology 2019; (12(10)):873-881 doi:10.1080/17474086.2019.1649132.

    PMID: 31343930
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    Ibrutinib Monotherapy in Symptomatic, Treatment-Naïve Patients With Waldenström Macroglobulinemia.

    Treon SP, Gustine J, Meid K, et al.

    Journal of clinical oncology : official journal of the American Society of Clinical Oncology 2018; (36(27)):2755-2761 doi:10.1200/JCO.2018.78.6426.

    PMID: 30044692
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    Long-Term Follow-Up of Ibrutinib Monotherapy in Symptomatic, Previously Treated Patients With Waldenström Macroglobulinemia.

    Treon SP, Meid K, Gustine J, et al.

    Journal of clinical oncology : official journal of the American Society of Clinical Oncology 2021; (39(6)):565-575 doi:10.1200/JCO.20.00555.

    PMID: 32931398
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    Lymphoplasmacytic lymphoma and marginal zone lymphoma in the bone marrow: paratrabecular involvement as an important distinguishing feature.

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    American journal of clinical pathology 2015; (143(6)):797-806 doi:10.1309/AJCP6ZODWV1CIDME.

    PMID: 25972321
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    Diagnostic value of bone marrow core biopsy patterns in lymphoplasmacytic lymphoma/Waldenström macroglobulinaemia and description of its mutational profiles by targeted NGS.

    Garcia-Reyero J, Martinez Magunacelaya N, Gonzalez de Villambrosia S, et al.

    Journal of clinical pathology 2020; (73(9)):571-577 doi:10.1136/jclinpath-2019-206282.

    PMID: 31980558
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    Prognostic factors and indications for treatment of Waldenström's Macroglobulinemia.

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    Impact of MYD88L265P mutation status on histological transformation of Waldenström Macroglobulinemia.

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    American journal of hematology 2020; (95(3)):274-281 doi:10.1002/ajh.25697.

    PMID: 31814157
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    How I use genomics and BTK inhibitors in the treatment of Waldenström macroglobulinemia.

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    PMID: 38211337

This page is for informational purposes only and does not constitute medical advice. Your hematologist or hematopathologist should interpret your bone marrow, IgM, and mutation results and guide your care.