A monoclonal B-cell lymphoproliferation in the vast majority of cases. It is characterized by a bimodal age distribution (15-30 years of life and late life). Epstein-Barr virus has been postulated to play a role in the pathogenesis of classical Hodgkin lymphoma. Morphologically, it is characterized by the presence of Reed-Sternberg cells and mononuclear Hodgkin cells. The Reed-Sternberg and mononuclear Hodgkin cells are CD30 positive in nearly all cases and CD15 positive in the majority of cases. Four histologic subtypes have been distinguished: lymphocyte-rich, nodular sclerosis, mixed cellularity, and lymphocyte-depleted classical Hodgkin lymphoma.