Prevalence of precancerous skin lesions and non-melanoma skin cancer in Japanese-Brazilians in Bauru, São Paulo State, Brazil Prevalência de lesões pré-neoplásicas e tumores cutâneos não melanomas em nipo-brasileiros residentes na cidade de Bauru, São Paulo, Brasil

Precancerous lesions and skin cancer are infrequent in Asians, and have received little documentation in the literature. Brazil has the world’s largest contingent of Japanese immigrants and their descendants, and 70% live in the State of São Paulo. The prevalence of such skin lesions in Japanese-Brazilians is unknown. This study aimed to assess the prevalence of actinic keratoses and non-melanoma skin cancer in first and second-generation Japanese-Brazilians over 30 years of age, without miscegenation, living in the city of Bauru, São Paulo State, in 2006. Of the 567 Japanese-Brazilians that underwent dermatological examination, actinic keratosis was diagnosed in 76, with a mean age of 68.9 years, and a single case of basal cell carcinoma was detected in a 39-year-old female patient. In Japan, prevalence of actinic keratosis varies from 0.76% to 5%, and the incidence of non-melanoma skin cancer is 1.2 to 5.4/100 thousand. Japanese-Brazilians from Bauru showed a 13.4% prevalence of actinic keratoses and earlier age at onset. Proximity to the Equator and a history of farming contribute to these higher rates. Presence of solar melanosis was associated with a 1.9-fold risk of developing actinic keratosis. Skin Neoplasms; Skin Manifestations; Solar Radiation Introduction Skin cancers are the most common malignant tumors in Brazil and the United States, where they account for 20%-30% of neoplasms in Caucasians, 2%-4% in Asians, and 1%-2% in Blacks 1. The worldwide incidence of non-melanoma skin cancer (basal cell carcinoma, squamous cell carcinoma, and Bowen’s disease) has increased by 4%-8% per year since 1960 2. Three million cases of non-melanoma skin cancer and 132 thousand melanomas are diagnosed worldwide each year 3. In Brazil, the number of new cases of non-melanoma skin cancer in 2006 was estimated at 55,480 in men and 61,160 in women. These figures correspond to an estimated risk of 61 new cases per 100 thousand men and 65 per 100 thousand women 4. In Japan, since 1987, the Japanese Skin Cancer Society has studied the epidemiology of malignant skin tumors. A recent national survey by this society showed a higher prevalence of basal cell carcinoma in the Japanese population and a non-melanoma skin cancer incidence of 1.2 to 5.4 per 100 thousand inhabitants 5,6,7. Since Caucasians have a lower concentration of melanin in the skin, they are more susceptible to skin damage from sun exposure. Melanin promotes the absorption of UVA and UVB rays, reducing the unwanted effects of solar radiation in this spectrum of the wavelength, responsible ARTIGO ARTICLE Ishioka P et al. 966 Cad. Saúde Pública, Rio de Janeiro, 25(5):965-971, mai, 2009 for the genesis of precancerous and malignant skin lesions. Actinic keratosis is a precancerous lesion with a 0.1%-20% conversion rate to squamous cell carcinoma 8,9,10. It occurs mainly in Caucasians that are chronically exposed to solar radiation and identifies groups at risk of developing skin cancer. Non-melanoma skin cancer is 70 times more frequent in individuals with light skin 1. Facilitating factors in the development of actinic keratoses and non-melanoma skin cancer are genetically determined. Other risk factors are immunosuppression and certain genetic disorders like xeroderma pigmentosum. Highly prevalent benign skin lesions such as solar melanosis, leukoderma punctatum, and solar elastosis also express actinic damage, and just as malignant skin lesions, they are more frequent in Caucasians. Chronic sun exposure in individuals with more skin pigment, as in Blacks and Asians, can also cause solar melanosis, leukoderma punctatum, actinic keratosis, and occasionally skin cancer. Epidemiological studies of actinic skin alterations in Asian and African descendants are poorly documented. Inconsistent recording of positive cases, together with low prevalence, hinder real estimates of their incidence. Non-Caucasians represent 30% of the United States population, and the Asian-descendant population in the Americas is estimated to increase by 36% in the coming years 11. In Brazil, of the total population of 169 million, 762 thousand are Asian-descendant and another 735 thousand are indigenous (Instituto Brasileiro de Geografia e Estatística. Censo Demográfico de 2000. http:// www.ibge.gov.br). Brazil has the world’s largest contingent of Japanese immigrants (and their descendants), and 70% of them live in the State of São Paulo 12. The prevalence of actinic keratosis and non-melanoma skin cancer in Japanese-Bra-