Transformation of de novo high-grade B cell lymphoma with MYC and BCL2 rearrangements to double-hit B lymphoblastic leukemia/lymphoma: a case report and review of literature

High-grade B cell lymphomas with MYC and BCL2 and/or BCL6 rearrangements (“double-hit” lymphoma (DHL)/“triple-hit” lymphoma (THL)) are mature B cell neoplasms with highly aggressive clinical behavior and poor response to therapy. Lymphoblastic transformation of mature B cell neoplasms is an uncommon event that is best recognized for follicular lymphoma (FL). To our knowledge, only one case of “B lymphoblastic” transformation of de novo DHL has been reported in the literature. Here, we describe another case of such transformation. The patient was a 57-year-old man who presented with hypercalcemia, high lactate dehydrogenase (LDH), and multiple lytic bone lesions and was diagnosed with high-grade B cell lymphoma with MYC and BCL2 rearrangements. The neoplastic cells were positive for CD45, CD19, CD20, CD79a, PAX5, CD10, BCL6, and BCL2 and negative for CD34, CD99, and terminal deoxynucleotidyl transferase (TdT). The patient received chemotherapy followed by autologous stem cell transplant and achieved complete remission. Nine months after the initial presentation, he developed general weakness and found to have cytopenias and circulating blasts. Bone marrow examination revealed extensive involvement by a high-grade B cell neoplasm co-expressing PAX5, CD10, and BCL2, in addition to precursor markers TdT and CD99. There was loss of CD20, CD79a, and BCL6 expression, and CD34 remained negative. A diagnosis of B lymphoblastic leukemia/lymphoma (B-LBL) was established. Similar MYC and BCL2 rearrangements were identified. IGH gene rearrangement studies confirmed clonal relatedness. The patient passed away 3 days after bone marrow examination. This case represents an extremely rare case of DHL transformation to B-LBL.