Malignant lymphoma is a heterogeneous category embracing three major types of lymphoid neoplasms: B cell neoplasms, T and NK cell neoplasms, and Hodgkin lymphoma. Within each type, distinct disease entities are defined based on a combination of morphology, immunophenotype, genetic features and clinical syndromes, the emphasis on which represents a new paradigm in the lymphoma classification of the World Health Organization (WHO). These lymphoma entities often have distinctive cytogenetic abnormalities, usually involving translocations that place a potential cellular oncogene under the influence of the immunoglobulin in some low-grade B-cell lymphomas. Both pathologists and oncologists are now concerned with better understanding each disease entity and its spectrum of morphology, genetic events, and clinical behaviors. Over the last decade, significant progress has been made in the molecular characterizations of mantle cell lymphoma, anaplastic large cell lymphoma, and marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT), which have not only provided insights into the pathogenesis of lymphomas, but also valuable data that could lead to therapies based on their clinical behavior.