Non-Hodgkin lymphoma (NHL) is the seventh most commonly diagnosed cancer in men and the ninth in women in the United States, with an estimated 66,360 new cases and 19,320 deaths from NHL in 2011. The disease represents approximately 4.2% of all cancer diagnoses (4.4% in males and 3.9% in females). The age-adjusted incidence of NHL overall was 19.8 in 2004-2008 in the United States. The incidence rates almost doubled between 1970 and 1990, and stabilized during the late 1990s. Some of this increase may be artifactual, resulting from improved diagnostic techniques and access to medical care, or directly related to the development of NHL in 25- to 54-year-old men with human immunodeficiency virus (HIV) infection. However, additional factors must be responsible for this unexpected increase in frequency of NHL that has been observed throughout the United States.The increases have been more pronounced in whites, males, the elderly, and those with NHL diagnosed at extranodal sites. Similar findings have been reported in other developed countries. In the United States, incidence rates increased significantly during 2001-2008 for marginal zone lymphoma (2.6% per year) and NK/T-cell lymphoma (5.7% per year) and decreased significantly for chronic lymphocytic leukemia/small lymphocytic lymphoma (-1.5% per year) and cutaneous T-cell lymphoma (-3.8% per year).
Epidemiology
Gender
The overall incidence of lymphoma is higher in men than in women. The age-adjusted incidence rate between 2004 and 2008 was 40% higher in males (24.0 per 100,000) than in females (16.5 per 100,000). Overall, NHL incidence rates remained unchanged during 1992–2001 among women but decreased at the rate of 1% per year among men, in part due to improved HIV treatment.
Age
The incidence of NHL overall and of most histologic subtypes rises exponentially with increasing age. In persons older than 65, the incidence was 91.1 per 100,000 persons in 2004-2008. Except for high-grade lymphoblastic and Burkitt lymphomas (the most common types of NHL seen in children and young adults), the median age at presentation for all subtypes of NHL exceeds 50+ years. Low-grade lymphomas account for 37% of NHLs in patients between the ages of 35 and 64 years at diagnosis but for only 16% of cases in those younger than age 35. Substantially higher rates were observed for diffuse large B-cell lymphoma (DLBCL) and Burkitt lymphoma among white and black men aged 25 to 54 years.
Race
The incidence of NHL varied by race, with non-Hispanic whites (21.6 per 100,000 persons) at higher risk than blacks (14.8 per 100,000), Asian-Americans (13.3 per 100,000), and Hispanics (15.4 per 100,000) during 2004-2008. Most histologies, particularly low-grade small lymphocytic and follicular lymphomas, are more common in whites than in blacks. Only peripheral T-cell lymphoma (PTCL), mycosis fungoides, and Sézary syndrome are more common in blacks than in whites.
Geography
NHL is most common in developed countries, with the United States having the highest rate worldwide. The lowest NHL rates are found in Eastern and south central Asia (2 to 3 per 100,000 population). Certain endemic geographic factors appear to influence the development of NHL in specific areas.
Human T-cell lymphotrophic virus-1 (HTLV-1)-associated adult T-cell lymphoma/leukemia (ATLL) occurs more frequently where HTLV-1 is endemic, in southern Japan and the Caribbean, and occurs sporadically in Brazil, sub-Saharan Africa, the Middle East, and the southeastern United States. The seroprevalence in southwest Japan is 16%, although the lifetime risk of ATLL for these persons is 2% to 6%.
The incidence of Burkitt NHL in Africa (Nigeria and Tanzania) is 6 to 8, compared with 0.4 in the United States. The clinical features of Burkitt lymphoma in Africa differ from those of cases reported to the American Burkitt Lymphoma Registry. Etiologic endemic factors include malaria as a source of chronic B-cell antigenic stimulation and Epstein-Barr virus (EBV)-induced immortalization of B lymphocytes.
Heavy-chain disease is a disorder of B-lymphoid cells characterized by diffuse thickening of the small intestine due to a lymphoplasmacytic infiltrate with secretion of incomplete IgA heavy chains. Pathologically, it is a mucosa-associated lymphoid tissue (MALT) lymphoma of the small bowel. This clinicopathologic entity is rarely encountered in individuals other than those of Mediterranean ethnic origin.
Follicular lymphomas are more common in North America and Europe but are rare in the Caribbean, Africa, China, Japan, the Middle East, and Latin America.
PTCLs are more common in Europe and China than in North America. They represent 7% to 12% of lymphomas in Western countries.
Disease sites
The NHLs are a heterogeneous group of neoplasms that usually arise or present in lymphoid tissues, such as lymph nodes, spleen, and bone marrow, but they may arise in almost any tissue. The most frequent sites for extranodal lymphomas, which constitute about 20% to 30% of all lymphomas (peripheral T-cell NHL, 70% to 80%; follicular, 8% to 10%), are the stomach, skin, oral cavity and pharynx, small intestine, and central nervous system (CNS). Although primary CNS lymphomas are rare, there has been a threefold increase in incidence, even if patients with HIV infection and other types of immunosuppression are excluded. Each of these sites may be involved singularly (ie, primary extranodal lymphoma) or as secondary extranodal sites concomitantly with other systemic disease.
Survival
The potential curability of NHL varies among the different histologic subtypes and is related in part to stage at presentation. The 5-year relative survival rate of patients with NHL increased from 47% between 1975 and 1977 to about 70% between 2001 and 2007. These improvements in survival occurred mainly in patients with intermediate- to high–grade histologies. The natural history (survival rates) for indolent lymphomas was unchanged from the 1950s to the early 1990s; however, recent data, including an analysis from Iowa of SEER data (1979–1999), showed improved overall survival rates for patients with follicular lymphoma.
