Trends during a half century in relative squamous cell carcinoma distribution by body site in the Swedish population: support for accumulated sun exposure as the main risk factor.

There is a strong relationship between squamous cell carcinoma (SCC) and exposure to ultraviolet radiation in terms of accumulated exposure. In this study, data from the Swedish Cancer Registry are surveyed to discern a reflection of behavioral and societal changes in relative distribution of SCC by body site. Data for the time period 1960-2004, including a total of 66 221 cases (56 669 people) were analyzed by body site for age and gender cohorts. The age-standardized (European population) incidence per 100 000 of SCC in the year 2004 was 30.4 in males and 15.4 in females. In the year 1960, the corresponding incidences were 7.7 and 3.8; that is, SCC has become four times more frequent in Sweden for both sexes during this period. The standardized incidence of SCC increased on all body sites except eyelids (men and women) and ears (women). Head tumors dominated among patients aged 70 years or more and diagnosed 1960-1964. Among patients less than 70 years old at diagnosis in 2000-2004, tumors of the trunk and limbs dominated. A relative increase of tumors of the scalp and neck was observed in all age groups (men), and of tumors of the trunk and upper limbs in all age groups and both sexes except among patients aged more than 90 years of age. In contrast, a relative decrease of tumors on the face (including the ears) was seen in all age groups. The relative increase of SCC of the trunk and upper limbs is a plausible reflection of intentional tanning.