The Non-Hodgkin’s Lymphomas

Abstract

Non-Hodgkin’ s lymphomas (NHLs) are malignant proliferations of the lymphoid tissues that can be distinguished from Hodgkin’s lymphoma (see Chapter 14) by a variety of clinical and histological features. NHLs are a disease of predominantly elderly persons, with a median age around 50–70 yr, are more heterogeneous in their behavior, and often have an extranodal involvement. The classification of NHLs continues to evolve. Recently, anew World Health Organization (WHO) classification scheme was introduced, which is based on the revised European American Lymphoma (REAL) classification and incorporates some of the progress in immunology and molecular biology (see “Classification”). Considerations that enter into these classifications are the lymphocyte lineage (B- vs T-cell type), and maturation status (precursor vs mature cell type), additional immunophenotypic markers, and characteristic molecular alterations. Based on these criteria, the clinical course and biology of each distinct lymphoma subtype may be more accurately predicted. About 90% of the NHLs are derived from a malignant B-cell, the remaining cases from T-cells, natural killer (NK) cells, or undifferentiated cells. In recent years, the incidence of NHL has steadily increased. NHLs are more frequent than Hodgkin’ s lymphoma and have an annual incidence of about 15–20 new cases per 100,000 people.