Richter's syndrome (RS), also known as Richter's transformation, is a transformation of B cell chronic lymphocytic leukemia (CLL) or hairy cell leukemia into a fast-growing diffuse large B cell lymphoma, a variety of non-Hodgkin lymphoma which is refractory to treatment and carries a bad prognosis. There is also a less common variant in which the CLL changes into a Hodgkin's lymphoma. [Source: Wikipedia 
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