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1570 Part XI: Malignant Lymphoid Diseases Chapter 95: General Considerations for Lymphomas 1571

Incidence of non-Hodgkin Lymphoma by calendar year Figure 95–2. Incidence of non-Hodgkin and Hodgkin
30 Male lymphoma by calendar year. The incidence of non-
Hodgkin lymphoma approximately doubled from the early
25
1970s to the mid-1990s in the United States and in other
Incidence rate (cases/100,000 population) 20 Female industrialized countries that tracked incidence of specific
cancers. No satisfactory explanation has been uncovered
for this change. The “epidemic” of lymphoma ended in the
15
mid-1990s and the incidence curves have been “flat” since
10
1996. The increase in incidence was present in Americans
women. In stark contrast and serving as an internal con-
trol, the incidence of Hodgkin lymphoma is essentially
0 5 of European and African descent and among men and
1975 1977 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 2005 2007 2009 2011 unchanged over that period of time. (Data from the Surveil-
lance, Epidemiology, and End Results (SEER) Program (www.
Year seer.cancer.gov) Research Data (1973-2011), National Cancer
Institute, DCCPS, Surveillance Research Program, Surveillance
Incidence of non-Hodgkin Lymphoma by calendar year Systems Branch, released April 2014, based on the November
4.5 4 Male 2013 submission.; 2014.)

3.5
Incidence rate (cases/100,000 population) 2.5 3 2 Female

1.5

0.5
0 1
1975 1977 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 2005 2007 2009 2011
Year

Follicular lymphoma represents approximately 25 percent of NHL solvents, have been found in one study or another to be more frequent
cases in the United States, but is very uncommon in many developing in lymphoma patients than “matched” healthy comparison groups. 21,26,27
countries and in Asia, especially in Japan and China. 21,22 The United The results often have been inconsistent from study to study. Expert
States has a higher incidence of all lymphomas than does Japan, whereas opinion indicates that no workplace exposure has been conclusively
the incidence of extranodal lymphoma is higher in Japan. 21,22 Burkitt linked to lymphoma, although farming or living in a community in
28
lymphoma occurs most frequently in sub-Saharan Africa, whereas which farming is prevalent has been a frequent association with higher
T-cell leukemia/lymphoma is most common in southwest Japan, the lymphoma incidence. 21,26,27
southeastern United States, northeastern South America, and the Many publications have reported a slightly increased familial
Caribbean basin. predisposition to the development of NHL, with an odds ratio of 1.5
The incidence of NHL increased dramatically in the last half of the in first-degree relatives of patients with NHL in a pooled analysis of
20th century in Europe, Asia, and in the United States. 20–22 From 1973 17 case control studies. 20,29–31 Nonsyndromic familial lymphoma refers
to 1990, inclusive, the increase in the United States was slightly more to apparently healthy family members, unlike syndromic familial lym-
than 80 percent, or approximately 4 to 5 percent per year (Fig.95–2). phoma in which immunodeficiency syndromes are the predisposing
The increase in incidence started after World War II, but the best data phenotype (e.g., Wiskott-Aldrich syndrome; see “Immunosuppres-
in the United States were acquired after 1972. The increase affected sion” below). The familial cases occur in different generations and
men and women, all age groups except children, and most histologic among enough family members to strongly suggest that a predispos-
types examined, though the greatest increase was in diffuse large ing unidentified gene results in an incidence above that in the popu-
B-cell lymphoma (DLBCL). The increased incidence per year reached lation at large. Li-Fraumeni syndrome is such an example, involving
a plateau in the early 1990s, except among women and older men germline mutations in p53. Alternatively, it is possible that family
21
where the incidence continued to rise. Hardell has hypothesized that members inherit a susceptibility to an unidentified environmental
new chemicals synthesized during and after World War II accounted lymphomagen.
for increased incidence trends, with subsequent improvements in
safety gear and regulatory restrictions resulting in stabilization in
the last decade. HIV was not prevalent in the human population ETIOLOGY AND PATHOGENESIS
23
when the increase first became apparent, although in later years HIV-
related lymphoma may have played a part in increasing incidence HISTOPATHOLOGIC HETEROGENEITY
rates. Orbital adnexal lymphoma and mantle cell lymphoma are Unlike other cancers, the malignancy referred to as “lymphoma” con-
exceptions to the recent plateau, with each still increasing at approxi- sists of nearly 80 phenotypes. Because each subtype of lymphoma
9
mately 6 percent a year. 24,25 exhibits unique nuances in its natural history, therapeutic consider-
Several occupations and industries and several potentially hazard- ations, and prognosis, unequivocal establishment of the precise subtype
ous exposures, such as pesticides, herbicides, dyes, engine exhausts, and of lymphoma is of paramount importance in a newly diagnosed patient.

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