Chronic lymphocytic leukemia and prolymphocytic leukemia. Two coins or two sides of the same coin?

摘要

Chronic lymphocytic leukemia (CLL) has a distinct morphology and immunophenotype. Despite lacking specific genetic abnormalities, the diagnosis is straightforward even in cases with atypical morphology. B-cell prolymphocytic leukemia (B-PLL) is a rare lymphoid neoplasm first described in 1974 as an aggressive variant of CLL. It differs from CLL in morphology and immunophenotype and it is recognized as a distinct entity in the World Health Organisation classification. Like CLL, B-PLL does not have recurrent genetic alterations although MYC abnormalities, TP53 mutations and complex karyotypes are frequent.1–3 The diagnosis of B-PLL relies on cytology, the immunophenotype and on investigations that rule out other splenomegalic B-cell neoplasms, particularly, mantle cell lymphoma (MCL). A debated issue is whether B-PLL represents the evolution of a CLL, particularly in cases with increased prolymphocytes (CLL/PL), or if it is a different entity. The differences in cytology, the immunophenotype and gene expression profile between CLL and B-PLL would argue against them being the same entity in two phases of disease evolution. 4