UCSF

Isolated MYC rearrangement without other recurrent genetic abnormalities is rare in B lymphoblastic leukemia/lymphoma (B-ALL/LBL), with most cases reported in pediatric patients. We report 3 adult cases with lymphoblasts showing a precursor B cell immunophenotype, and isolated MYC/IGH translocation. All 3 cases occurred in male patients with initial presentation of diffuse lymphadenopathy. Cases 1 and 2 had B-ALL with significantly increased lymphoblasts in peripheral blood and bone marrow. Case 3, a patient with human immunodeficiency virus infection, had the diagnosis of B-LBL made on a retroperitoneal lymph node biopsy and had no peripheral blood or bone marrow involvement. The leukemic and lymphoma cells in all 3 cases demonstrated Burkitt lymphoma-like morphology with deeply basophilic cytoplasm and numerous cytoplasmic vacuoles. However, all 3 had immature immunophenotypes including expression of terminal deoxynucleotidyl transferase (TdT), absence of BCL6, and dim-to-negative CD45. CD20 was largely negative in 2 of 3 cases. All 3 had confirmed MYC/IGH translocation, but lacked rearrangements of BCL2 or BCL6. EBV was negative by Epstein-Barr virus encoded small RNA in situ hybridization. Treatment protocols varied, including both high-risk ALL-type (protocol 8707) and high-grade lymphoma regimens (hyper-CVAD [cyclophosphamide, vincristine, adriamycin, and dexamethasone]), but no patient achieved continuous complete remission. These cases seem to represent a distinct biological phenomenon, in which a MYC translocation may be acquired at an immature stage of differentiation, thus manifesting features of both B-ALL/LBL and Burkitt lymphoma.