Cases that have been labeled as B-PLL include: (1) a variant of mantle cell lymphoma, characterized by presence of IGH::CCND1; (2) prolymphocytic progression of CLL/SLL, defined by CD5-positive non-mantle B-cell neoplasm with >15% prolymphocytes in the peripheral blood and/or bone marrow [44–47], and (3) other cases, now classified as “splenic B-cell lymphoma/leukaemia with prominent nucleoli”. The gene discussed is CD5; the disease is B-cell prolymphocytic leukemia.