Double- and triple-hit lymphomas can present with features suggestive of immaturity, including TdT expression, and create diagnostic challenges.

Double- and triple-hit lymphomas (DHL/THL) are aggressive B-cell neoplasms characterized by translocation of MYC with concurrent BCL2 and/or BCL6 translocation. In this retrospective study from one institution, we report clinicopathologic features of 13 cases (9 DHL/4 THL). The median age was 59 years (range 30-74) and patients included eight females and five males. Presentation included enlarging lymphadenopathy/masses (11 patients) and abnormal peripheral blood findings (2 patients). Features which raised the differential of an immature neoplasm included terminal deoxynucleotidyl transferase positivity (four cases, two THL/two DHL); dim CD45 expression (seven cases), lack of CD20 (two cases), or lack of surface immunoglobulin light chain (three cases) by flow cytometry; and blastoid morphology (two cases). We conclude that expression of TdT in a B-cell lymphoma with mature features or expression of surface light chain in a case otherwise suggestive of B-lymphoblastic leukemia/lymphoma should prompt an expedited evaluation for DHL/THL.