Lymphoid malignancies include nearly 40 named entities; however, they can be divided into roughly five large categories based on the clinical syndrome they cause: acute lymphoid leukemias, chronic lymphoid leukemias, non-Hodgkin's lymphomas, Hodgkin's disease, and plasma cell disorders (chiefly multiple myeloma). In 2007, 111,820 people were diagnosed with a lymphoid malignancy and 36,440 patients died from a lymphoid malignancy. Figure 104-1 shows a distribution of the annual incidence in a pie chart. Acute and chronic lymphoid leukemias are covered in a separate chapter. We shall discuss non-Hodgkin's lymphomas, Hodgkin's disease, and plasma cell disorders in this chapter.
Distribution of lymphoid malignancies in the United States.
The non-Hodgkin's lymphomas (NHLs), the most common lymphoid malignancies, are a heterogeneous group of cancers that have in common the clonal expansion of cells of lymphoid origin. The heterogeneity stems from the very large number of distinct lymphocyte subsets and diverse molecular and genetic pathways to neoplasia. Mutations, chromosome translocations, or other alterations in certain genes (e.g., BCL2, c-MYC, FAS, BCL6) contribute to the pathogenesis in many cases and gene expression profiling has identified subsets of NHL with varying aggressiveness and response to chemotherapy. About 88% of all NHLs are derived from B cells. Despite insights into the alterations associated with specific NHL types, the mainstay of current therapy remains empiric and typically includes cytotoxic chemotherapy combined with monoclonal antibody directed at the CD20 molecule, which is expressed on nearly all B cells. Clinical trials suggest that elderly patients may safely receive these agents with expectations similar to their younger counterparts.
In 2007, 63,190 new cases of NHL were diagnosed and about half occurred in persons aged 60 years or older. National Cancer Institute data indicates an approximate 25% increase in NHL incidence since 1950, although there is some evidence that the rate of rise has declined somewhat since 1990. Although some of the increase can be related to the acquired immunodeficiency syndrome (AIDS) epidemic, particularly in young and middle-aged persons, the bulk of the cause of the increase is undefined, particularly in the aged population. With more effective human immunodeficiency virus (HIV) treatment, HIV-associated lymphoma is becoming less frequent. However, NHL affects older patients (one third are 70 years or older) and is the fifth leading cause of cancer deaths in women aged 80 years and older. Furthermore, current cancer surveillance statistics indicate that despite the fact that incidence is declining for the population as a whole, for those aged older than 65 years, there is a net increase of 1.3% compared to a rate of −1.5% for the younger population.
Lymphoma classification was a contentious field until 1999 when the World Health Organization Classification was developed by an international panel of hematopathologists and clinicians based on consensus criteria including histology, immunology, genetics, and ...