Chronic lymphocytic leukaemia/small lymphocytic lymphoma and mantle cell lymphoma: from early lesions to transformation

Abstract

The International Clinical Advisory Committee reviewed advances in our understanding of the clinicopathologic and biologic features of chronic lymphocytic leukaemia/small lymphocytic lymphoma, B-cell prolymphocytic leukaemia, and mantle cell lymphoma since the revised 4th edition of the WHO Classification of Tumours of the Haematopoietic and Lymphoid Tissues. Discussions amongst pathologists, clinicians, and molecular geneticists around these diseases focussed on incorporating new knowledge into the next classification system. In this manuscript, we review these disease entities and incorporate results of these deliberations, including advances in our understanding of early lesions and transformation.

Mature B, T and NK-cell, plasma cell and histiocytic/dendritic cell neoplasms: classification according to the World Health Organization and International Consensus Classification

“…The entity of B-cell prolymphocytic leukemia (B-PLL) has been eliminated in WHO-HAEM5, with the idea that cases diagnosed as B-PLL actually represent mantle cell lymphoma with leukemic involvement, chronic lymphocytic leukemia with prolymphocytic progression, or a primary splenic lymphoma with cytomorphology reminiscent of prolymphocytes (see below). The ICC requires > 55% prolymphocytes in the peripheral blood for a diagnosis of B-PLL ( 9 ) and restricts the diagnosis of B-PLL to cases in which transformed chronic lymphocytic leukemia, splenic marginal zone lymphoma, mantle cell lymphoma and hairy cell leukemia variant can be excluded. ( 2 ) Although the ICC does not explicitly define criteria for prolymphocytic transformation of CLL, it does state that “In addition to CLL, transformation to a neoplasm with prolymphocytic features has been described in rare cases of splenic marginal zone lymphomas”, indicating that the ICC does indeed recognize prolymphocytic transformation of CLL.…”

“…( 2 ) Although the ICC does not explicitly define criteria for prolymphocytic transformation of CLL, it does state that “In addition to CLL, transformation to a neoplasm with prolymphocytic features has been described in rare cases of splenic marginal zone lymphomas”, indicating that the ICC does indeed recognize prolymphocytic transformation of CLL. ( 9 ).…”

“…( 10 – 12 ) ICC describes two types of Hodgkin lymphoma-like Richter transformation of CLL: type 1, in which Hodgkin-Reed-Sternberg (HRS) cells are present in a background of CLL/SLL, and type 2, in which HRS cells are found in the mixed inflammatory background typical of sporadic classic Hodgkin lymphoma. ( 9 , 13 ) Optimal management of such cases is not yet defined. ( 14 ) As the concept of HRS cells without a Hodgkin-like background infiltrate as transformation is considered preliminary, WHO-HAEM5 continues to require a non-neoplastic microenvironment similar to that in sporadic classic Hodgkin lymphoma to establish a diagnosis of Hodgkin lymphoma-like Richter transformation.…”