Microscopic subtypes and smoking habits

Cancers that originate from lung cells can be divided into two groups, small cell lung cancers (SCLC) and non-small cell lung cancers (NSCLC), according to their microscopic characteristics. NSCLC's include squamous cell carcinoma (SQC), large-cell carcinoma (LCC) and adenocarcinoma (AD). Tobacco smoking causes all types of lung cancer, but predominantly increases the incidence of SQC. The incidence of this subtype is therefore more sensitive to the history of smoking in any given population.
The AD subtype dominates among non-smokers. It therefore appears to be more common among European women who took up the smoking habit considerably later than men.
The relative frequency of the different subtypes is therefore strongly influenced by the prevalence, duration and intensity of tobacco smoking in the population. For men, the typical distribution by subtype is 15% SCLC, 23% AD and 41% SQC. For women, it is 13% SCLC, 40 % AD and 23 SQC.