B-Cell Acute Lymphoblastic Leukemia Associated with Isolated and Recurrent Central Nervous System Relapse with a Novel t(6;19)(q21;p13) Translocation: A Case Report

Abstract

B-cell acute lymphoblastic leukaemia (B-ALL) is a haematological malignancy characterised by the clonal proliferation of B-lymphoid precursors. Cytogenetic and molecular alterations are central to B-ALL classification and diagnosis according to the 2024 World Health Organization (WHO) guidelines. Although recurrent abnormalities are well characterised, rare chromosomal alterations may provide insights into leukaemogenesis and prognosis. Here, we report the case of a 33-year-old woman diagnosed with B-ALL. Bone marrow flow cytometry identified 82% blasts expressing CD19, CD79a, CD22, and CD10, with partial cytoplasmic IgM and nuclear TdT expression and absence of CD34, consistent with B-precursor ALL. BCR::ABL1 p190 and p210 transcripts were negative by nested RT-PCR. Cerebrospinal fluid (CSF) flow cytometry detected 4.9% immature B cells with a phenotype similar to bone marrow blasts, confirming central nervous system (CNS) involvement at diagnosis. Conventional cytogenetics revealed 46,XX,t(6;19)(q21;p13). The patient received Hyper-CVAD chemotherapy and intrathecal therapy, achieving complete bone marrow remission with undetectable measurable residual disease and a normal karyotype. Subsequent CSF assessments were negative for leukaemic involvement. Three isolated CNS relapses occurred at 7, 11, and 17 months after diagnosis, with 82.7%, 95.9%, and 5.1% leukaemic cells in the CSF, respectively, despite treatment with intrathecal chemotherapy and CNS radiotherapy. The patient died 20 months after diagnosis. This case expands knowledge of rare cytogenetic abnormalities in B-ALL and highlights the need for further studies to clarify the biological and potential prognostic implications of t(6;19)(q21;p13).