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Published on: June 29, 2016
[MALT lymphoma accompanied by elevated serum IgM levels mimicking Waldenström's macroglobulinemia]
Shintaro Izumi1, Kenji Kimura1, Yusuke Takeda1
1Department of Hematology, Chiba University Hospital.
Insights
This case study highlights a patient diagnosed with extranodal marginal zone lymphoma (MALT lymphoma) despite high IgM levels, a condition often mistaken for Waldenström's macroglobulinemia. Accurate diagnosis was achieved through genetic analysis, emphasizing the importance of the MYD88 L265P mutation test.
Area of Science:
- Hematology
- Oncology
- Immunology
Background:
- Chronic hepatitis C can present with elevated serum IgM and monoclonal protein.
- Distinguishing between Waldenström's macroglobulinemia and other IgM-producing B-cell lymphomas is clinically significant.
Observation:
- A 60-year-old male with chronic hepatitis C presented with markedly elevated serum IgM and monoclonal protein.
- Imaging revealed pulmonary masses, renal and bladder abnormalities, while biopsy showed CD138+, IgM+, IgH-MALT1+ lymphocytes and plasma cells.
- The MYD88 L265P mutation, typically found in Waldenström's macroglobulinemia, was negative.
Findings:
- The patient was diagnosed with extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma), not Waldenström's macroglobulinemia, based on IgH-MALT1 translocation and absence of MYD88 L265P mutation.
- Treatment with rituximab + CHOP therapy resulted in complete remission.
- The MYD88 L265P mutation analysis is crucial for differentiating IgM-related hematopoietic malignancies.
Implications:
- Accurate diagnosis of IgM monoclonal gammopathies requires comprehensive genetic testing beyond IgM levels.
- MYD88 L265P mutation status is a key differentiator in IgM-associated B-cell lymphoproliferative disorders.
- This case underscores the diagnostic utility of molecular markers in complex hematologic malignancies.
Abstract:
A 60-year-old man with chronic hepatitis C was referred to our hospital with significantly elevated total protein and serum IgM (9,500 mg/dl) levels identified via a routine checkup. Blood examination revealed increased serum IgM-monoclonal protein and serum-soluble IL-2 receptor (sIL2R) levels. Computed tomography and fluorodeoxyglucose positron emission tomography revealed pulmonary masses, abnormal soft tissue masses surrounding the bilateral kidneys, and thickened mucous membrane of the bladder with high fluorodeoxyglucose uptake. Pathological examination of the pulmonary mass revealed infiltration of medium-sized lymphocytes and plasma cells. Immunohistochemical analysis revealed tumor cells positive for CD138 and IgM, with a low positive rate of Ki-67 expression. Notably, the tumor cell-surrounding lymphocytes were positive for CD20. Although the patient was initially regarded as having Waldenström's macroglobulinemia owing to the significantly increased serum IgM levels, based on positive IgH-MALT1 translocation and negative MYD88 L265P mutation findings, he was further diagnosed with extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma). Complete remission was achieved following six cycles of rituximab + CHOP therapy. This study data suggest that analysis of the MYD88 L265P mutation in tumor cells is suitable for accurately diagnosing hematopoietic malignancies with increased IgM monoclonal protein.
