The problem of timely diagnosis and effective treatment of EBD-associated lymphoproliferative diseases is associated with a large variety of morphological and immunological manifestations, which require a powerful, highly specific immunohistochemical and molecular genetic research methods for the correct assessment. The article elucidates current information about the pathogenesis of oncogenic EBV infection, the main clinical forms of associated lymphoproliferative processes, their main diagnostic criteria. The given clinical case of angioimmunoblastic T cell lymphoma clearly demonstrates the complexity of the diagnostic process, underestimation of informativity and the importance of molecular genetic research, which led to the rejection of chemotherapeutic treatment, the rapid progression of the terminal stage of lymphoproliferative disease with the development of polyorganic failure and lifetime destruction, necrosis of the structural components of the tumor, as a result of which during the autopsy of morphological signs of lymphoma was not detected.