Classical Hodgkin lymphoma and its differential diagnoses

Classical Hodgkin lymphoma (CHL) is a unique type of B-cell lymphoma defined by the presence of characteristic neoplastic cells, termed Hodgkin- and Reed-Sternberg cells, in an exuberant inflammatory background. CHL constitutes 15–20% of malignant lymphomas. Modern treatment modalities are able to cure the majority of patients. Despite the presence of clonal immunoglobulin gene rearrangements, the tumour cells lack a B-cell-specific expression program and show a phenotype devoid of most B-cell antigens, with CD30 and CD15 as characteristic markers. Although most cases of CHL can be diagnosed readily by morphology and a limited panel of immunohistochemical markers, a variety of malignant lymphomas and reactive conditions can imitate CHL, and true borderline cases with features intermediate between CHL and large B-cell lymphoma exist. This review summarizes the diagnostic criteria and relevant biological features of CHL and describes the most important differential diagnoses, including lymphocyte predominant Hodgkin lymphoma.