BRAF V600E-mutated marginal zone lymphoma may exhibit features that partially overlap with hairy cell leukemia.
Jason Love, Tanvi Verma, Phil Palmer et al.
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Case in brief
This report describes two cases of BRAF-mutated marginal zone lymphoma (MZL), including a nodal MZL (NMZL) with a BRAF V600E mutation that exhibited partial morphologic and immunophenotypic overlap with hairy cell leukemia (HCL). Despite these overlaps, the absence of specific markers allowed for accurate classification as NMZL. The findings highlight the importance of comprehensive diagnostic approaches.
What made this case unusual
The NMZL case demonstrated features that partially overlapped with hairy cell leukemia, including strong CD25 and CD123 expression, which is atypical for MZL.
Diagnostic / clinical pearl
Clinicians should be aware that BRAF V600E mutations in small B-cell lymphomas may not be pathognomonic for hairy cell leukemia and must be interpreted in conjunction with morphologic and immunophenotypic findings.
Why it matters
This case emphasizes the need for integrating BRAF testing in the diagnostic workup of small B-cell lymphomas to avoid misclassification and to identify potential targetable mutations.