Adenocarcinoma tends to have a worse prognosis than squamous cell cancer in all stages. The histologic distinction between non-small cell lung cancer and small cell lung cancer is extremely important. There are substantial differences between the two groups in both treatment and prognosis. In general, small cell lung cancer tends to be more aggressive and spreads sooner to distant sites. Yet small cell lung cancer also is inclined to be more responsive to chemotherapy and chest radiotherapy.
Smoking is the major risk factor for the development of small cell lung carcinoma.
In smokers, lung cancer usually is associated with three principal histologic types - small cell carcinoma, squamous cell carcinoma, and adenocarcinoma. Small cell cancers are reduced in linear proportion to the number of years since quitting. Among certain racial groups, such as Asians, the distribution of adenocarcinoma in nonsmokers is similar to that in smokers, although the rate of lung adenocarcinoma is also much higher in Asian than in Western populations. In Hong Kong, there is a very high rate of adenocarcinoma among Chinese women. In addition, the rate of adenocarcinoma in Koreans is increasing in both sexes, especially among nonsmokers.