CD19 and B-cell chronic lymphocytic leukemia: CLL is defined, in accordance with the World Health Organization and International Consensus Classification Clinical Advisory Committee’s 2022 Classification of Lymphoid Neoplasms updates, as a low-grade lymphoproliferative neoplasm with ≥5 × 109/L clonal B cells in the peripheral circulation expressing CD5, CD19, CD20(dim), and CD23 [2,3].