Descriptive Epidemiology

HL is an uncommon cancer, with approximately 8000 new cases diagnosed in the United States annually.5 Several large epidemiologic reports have noted that males have a slightly higher incidence of HL than do females; that whites are at higher risk than are blacks; and that HL seems to be more common in patients of higher socioeconomic class than in those of lower socioeconomic class.6-11

HL is associated with a bimodal age-specific incidence distribution. The first peak occurs in early adulthood, beginning at ages 10-14, peaking at ages 20-24, and decreasing at age 40-44. The second peak begins at age 50 and increases over time. Forty-one percent of cases are diagnosed in patients aged 20-34.6

Nodular sclerosing (NS) HL accounts for the majority of histologic subtypes of HL associated with the early-age incidence peak. NS HL has an essentially unimodal age-specific incidence, with a peak in young adults aged 20-24. The age-specific incidence rate for NS HL falls off by age 40-44, then remains relatively constant between the ages 45 and 64. Mixed cellularity HL has a unimodal age distribution, its incidence increasing slowly with age. By the age of 50, mixed cellularity has been reported to be the most common histologic subtype of HL.6 Lymphocyte-depleted HL is rare in younger patients, and progressively increases with age.

HL is more common in first-degree relatives.12-16 Some data suggest that siblings have a two- to fivefold increased risk of developing HL; same sex siblings may have up to a ninefold risk.16 When HL occurs in families, it is more likely to involve males. Some early reports suggested that HL may be contagious, particularly by airborne transmission, although subsequent studies conclusively refuted this possibility.17-19 Certain HLA antigens, particularly HLA-DP, have been associated with an increased incidence of HL and with clinical outcome.20-22

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