A Novel t(10;22) Translocation Harboring an IGL Gene Deletion in a CLL Patient Transforming to B-PLL with 1q Gain.

Objectives: We report on a rare case of B-cell prolymphocytic leukemia (B-PLL) in a patient with a history of chronic lymphocytic leukemia (CLL) that showed a novel translocation t(10;22)(q21;q11.22) and an interstitial deletion of 11q14.1-q23.3 in 2017. The chromosome microarray analysis (CMA) confirmed the 11q22 deletion and revealed a small interstitial deletion of IGL gene. In 2018, the patient presented with worsening lymphocytosis, anemia and thrombocytopenia. The peripheral blood smear revealed an increased prolymphocyte population, which comprised 60.4% of lymphoid cells, establishing a diagnosis of B-cell prolymphocytic leukemia. The CMA and G-banded chromosome analysis showed one additional aberration in the form of 1q gain translocated onto the other homologue 22. These findings suggested clonal evolution of CLL to B-PLL. The most common translocation involving immunoglobulin lambda chain (IGL) in CLL is the t(18;22), followed by t(8;22) and (11;22). An evolution to B-PLL occurs in most cases without gaining additional aberrations. Here, we report for the first time a novel translocation involving IGL with chromosome 10q21 and one 1q gain occurring in a patient with CLL that transformed to B-PLL. Based on the disease progression and this newly developed cytogenetic aberration, our case supports the progressive nature of CLL in the presence of IGL deletion and suggests the pathological role of 1q gain in CLL transformation.