ABSTRACT

Once a rare disease, lung cancer has become the most common type of lethal cancer throughout the world. This change has occurred since the 1920s , when it was observed both in Europe and in North America that the number of the cases began to increase. Although mentioned sporadically in the medical literature in the first half of the century, it was in 1950 that several well-performed case-controlled studies first suggested tobacco smoking as the overwhelming cause of lung cancer. It took even more years before results of large prospective studies, like the pioneering work of Doll and Hill, convinced both the public and the governments that smoking is the most important cause of the disease. Histologically, lung cancer is divided into four major subgroups: squamous-, adeno-, small cell, and large cell carcinomas. In a substantial number of cases, however, accurate histological diagnosis may be difficult, due to both intrinsic tumor heterogeneity and to inter-observer variability. Kreyberg suggested that only squamous and small cell carcinomas were caused by tobacco smoking, but most of the more recent studies indicate that the majority of adenocarcinomas is also caused by tobacco smoking. In all studies the proportion of adenocarcinoma is much higher in females than in males and secular trends during 1980s and 1990s have shown an increase in the occurrence of adenocarcinoma. Most occupational carcinogens, with the exception of chloromethyl ethers and radiation (radon), which have a higher tendency to promote small cell lung cancer, give rise to tumors with a histological distribution that is similar to tumors caused by tobacco smoke.

Keywords: Lung cancer. Epidemiology.

RESUMO

O câncer do pulmão, de doença rara no início do século XX, tornou-se a neoplasia mais letal em todo o mundo. Essa mudança se iniciou na segunda década do século, quando se observou que o número de casos vinha aumentando em todo o mundo. Somente na década de 1950 os trabalhos da literatura demonstraram, pela primeira vez, que o aparecimento do câncer do pulmão estava relacionado intimamente ao tabagismo. Foram necessários mais 10 anos para que os trabalhos de Doll e Hill convencessem o público e as autoridades de que o tabagismo era a mais importante causa da doença. O câncer do pulmão é dividido em quatro diferentes tipos: escamoso, adenocarcinoma, carcinoma de pequenas células e carcinoma de grandes células. Atualmente, sabe-se que tanto o carcinoma escamoso quanto o carcinoma indiferenciado de pequenas células e o adenocarcinoma estão relacionados com o tabagismo. A maioria dos carcinógenos ocupacionais dá origem a tumores do pulmão com distribuição histológica semelhante àquela causada pela fumaça do tabaco.

Palavras-chave: Câncer do pulmão. Epidemiologia.

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