Abstract: | Available are three cases of Richter's syndrome, i.e. immunoblastic lymphosarcoma with plasmocytic differentiation which developed in patients with chronic lymphocytic leukemia and prolymphocytic (lymphocytic) lymphosarcoma. Clinical, anatomical and autopsy findings are analysed. The immunoblastic lymphosarcoma is suggested to arise either because of transformation of the tumor prolymphocytes (lymphocytes) due to the disease progression or can be promoted by a second tumor. |