MYD88 L265P Somatic Mutation Its Usefulness in the Differential Diagnosis of Bone Marrow Involvement by B-Cell Lymphoproliferative Disorders

Objectives: To examine the usefulness of the MYD88 L265P somatic mutation in identifying cases of lymphoplasmacytic lymphoma (LPL) from other lymphoplasmacytic neoplasms in bone marrow biopsy specimens. Methods: We studied 64 bone marrow biopsy specimens with involvement by various small B-cell lymphomas or plasma cell myeloma. Results: The MYD88 L265P somatic mutation was present in 13/13 cases of LPL, 1/13 cases of hairy cell leukemia, and absent in the other mature B-cell neoplasms tested. A test set of diagnostically challenging bone marrow cases with lymphoplasmacytoid morphology (B-cell lymphoma, not otherwise specified) was selected for additional review and reclassified, without knowledge of the MYD88 L265P status. Of those 16 cases, 7 were positive for MYD88, including 4/4 cases that were reclassified as LPL during the review. Conclusions: Although not entirely specific, MYD88 L265P is a useful adjunct for bone marrow diagnosis in separating LPL from other small B-cell lymphomas and plasma cell myeloma.