Richter transformation in the brain from chronic lymphocytic leukemia.

Richter syndrome (RS) involves the development of an aggressive lymphoma in patients with chronic lymphocytic leukemia (CLL). Diffuse large B-cell lymphoma (DLBCL) is the most common type of RS. Extranodal RS occasionally occurs; however, isolated lesions in the central nervous system (CNS) of RS are rarely seen and the features have not been well described. We describe a Japanese patient who developed isolated involvements of the parenchyma of the CNS as a manifestation of RS two years after the initial diagnosis of CLL. DLBCL in the cerebrum was confirmed to be clonally related to the CLL cells by immunoglobulin heavy chain (IGH) gene analysis, utilizing the identical VH-D-J regions with additional mutations in the IGH variable region.