Since adenocarcinomas begin in the glandular cells of several internal organs, according to the National Institutes of Health, their causes are varied. An adenocarcinoma of the lung, for example, can be caused by smoking or being exposed to second-hand smoke, says the National Cancer Institute.
Other risk factors for adenocarcinoma of the lung are being exposed to asbestos and other toxins or being exposed to radiation during therapy to treat diseases of the chest or the breast, says the NCI. People are also at higher risk for lung cancer if they live in an area with air pollution or are HIV-positive. Heavy smokers who take beta-carotene supplements are also at higher risk for lung adenocarcinoma.
Things that put a patient at higher risk for adenocarcinoma of the pancreas also include smoking, says the Center for Pancreatic and Biliary Diseases. The risk of this type of cancer is also increased if a person has a diet high in meats and fats, if he has diabetes, and if he suffers from chronic pancreatitis, or an inflammation of the pancreas that has lasted a long time. Pancreatic cancer also seems to have a genetic component in some families.
Though the causes or at least the risk factors for pancreatic and lung cancers are at least partially known, the causes of such cancers as prostate and breast cancer remain largely unknown, says the American Cancer Society.