Introduction

Beginning in mid-century, a pandemic of lung cancer affected the industrial countries of Europe and North America, later spreading to nearly all other nations. This was due to the increasing widespread use of tobacco.

Histology, classification and diagnosis

Lung cancer can be classified into four major histological types, which have been shown to have etiological significance (IARC, 1988). As interpretation of epidemiological findings has been hampered by variations in nomenclature and criteria, the WHO Classification should be followed (Table 34.1).

The association with cigarette smoking is strongest for squamous cell carcinoma (and its variants), and least for adenocarcinoma. The proportion of the histological types changes according to sex and age group. It is also influenced by the source of biopsy, since peripheral tumors are more likely to be adenocarcinomas. There is evidence that the small (oat) cell type of carcinoma is a biological entity associated with the ras oncogene, and possibly a human papilloma virus (HPV).

Descriptive epidemiology

Incidence

Large international variations are seen (Fig. 34.1 and Appendix 1). In 1980, lung cancer was globally estimated to comprise one in ten of all newly diagnosed cancers for both sexes combined and was the most common tumor in males. The highest rates (100 to 110) are observed in the US black population, in New Zealand Maoris and in Scotland.