Richter's transformation

Richter's transformation (RT), also known as Richter's syndrome, is the conversion of chronic lymphocytic leukemia (CLL) or its variant, small lymphocytic lymphoma (SLL), into a new and more aggressively malignant disease. CLL is the circulation of malignant B lymphocytes with or without the infiltration of these cells into lymphatic or other tissues while SLL is the infiltration of these malignant B lymphocytes into lymphatic and/or other tissues with little or no circulation of these cells in the blood. CLL along with its SLL variant are grouped together in the term CLL/SLL. RT is diagnosed in individuals who have CLL/SLL that converts to a malignancy with the microscopic histopathology of diffuse large B-cell lymphoma (DLBCL) or, less commonly, Hodgkin’s lymphoma (HL). There are rare cases of: 1) CLL/SLLs that convert into lymphoblastic lymphoma, hairy cell leukemia, or a high grade T cell lymphoma such as anaplastic large-cell lymphoma or angioimmunoblastic T-cell lymphoma; 2) CLL/SLLs that convert into acute myeloid leukemia; 3) CLL/SLLs that convert into or develop non-hematological malignancies such as lung cancer, brain cancer, melanoma of the eye or skin, salivary gland tumors, and Kaposi's sarcomas; and 4) conversion of follicular lymphoma, lymphoblastic lymphoma, or marginal zone lymphoma into other types of hematological malignancies. While some of these conversions have been termed RTs, the World Health Organization and most reviews have defined RT as a conversion of CLL/SLL into a disease with DLBCL or HL histopathology. Here, RTs are considered to be CLL/SLLs which convert into a disease with either DLBCL histopathology (here termed DLBCL-RT) or Hodgkin's lymphoma histopathology (here termed HL-RT). CLL/SLL is the most common adult leukemia in Western countries, accounting for 1.2% of the new cancers diagnosed each year in the United States. It usually occurs in older adults (median age at diagnosis 70) and follows an indolent course over many years. About 1-10% of CLL/SLLs develop a Richter's transformation at a rate of 0.