Women have always had a higher incidence of adenocarcinoma than the other lung cancer types. Men used to have a higher incidence of squamous cell tumours than other tumour types. However, in the last decade, the adenocarcimonas have been the most frequent tumour type. Men still have squamous cell tumors more frequently than women.
How are lung tumours related to smoking?
Squamous cell cancer begins in the larger bronchial tubes of the lung and metastasizes through the lymph system. The incidence of squamous cell is decreasing but there is evidence that both males and females with squamous cell cancer smoked more intensely than patients with other histological types.
Adenocarcinoma begins in the peripheral lung zones and spreads via the blood stream. Unlike squamous cell cancer, adenocarcinoma is increasing in incidence. Researchers have postulated that this trend is due to the effects of smoking filtered cigarettes.
Squamous cell and small cell lung cancer is caused by inhalation of large particle carcinogens, like those inhaled by smokers of unfiltered cigarettes. Large particles of inhaled tobacco smoke are deposited along the central bronchial tubes of the lungs, which is where the cancer initiates.
Adenocarcinoma is caused by smaller particles that pass through a cigarette filter. These smaller particles are distributed in the smaller and remote airways of the lungs where the cancer initiates.
In the past, women have been more likely than men to smoke filtered cigarettes, and this may account for the higher incidence of adenocarcinoma. It is important to know that, in addition, there has always been a significant incidence of adenocarcinoma in non-smoking women.