About Lung Cancer
Lung cancer is one of the leading causes of cancer death in the world in both men and women, but it is also one of the most preventable kinds of cancer. Almost 80% of cases are associated with cigarette smoking, and the cause-and-effect relationship has been extensively documented.
Lung tumours almost always start in the tubular - the spongy, pinkish gray walls of the bronchi. Researchers have identified more than 20 different types of cancerous tumours that originate in the lung itself which may lead to primary lung cancer. The major types include small-cell lung cancer and non-small cell lung cancer. The non-small cell cancers are further classified into squamous cell carcinoma, adenocarcinoma, and large-cell carcinoma. At time, mixed tumours may also occur.
Non-Small Cell Lung Cancer
Squamous cell carcinoma usually starts in cells of the central bronchi, more commonly in men and in smokers and accounts for approximately 30% of all lung cancers. Luckily, it is the easiest to detect early, as its distinctive cells are likely to show up in tests of mucus samples. Furthermore, it also tends to be most curable if detected early since it spreads relatively slowly and often times confined to the lung.
Adenocarcinoma is the most common type of lung cancer accounting for 40% of all lung cancers. It is most commonly seen in women and non-smokers and tends to originate along the outer edges of the lungs in the smaller airways. This kind of cancer is difficult to detect early as it often spreads to spaces between the lungs and the chest wall.
Large-cell carcinomas are a group of cancers with large, abnormal-looking cells that tend to originate along the outer edges of the lungs accounting for 10%-15% of all cases. However, this type of tumour has a high tendency to spread to nearby lymph nodes and distant sites.
Small Cell Lung Cancer
Small-cell lung cancer is the most aggressive form of lung cancer. Similar to like squamous cell carcinoma, this cancer usually originates in the large, central bronchi and spreads quickly displaying minimal symptoms, making it particularly threatening. In fact, at the time of detection close to 75% of the patients with this type of cancer have metastasis that frequently spreads to the liver, bone, and brain. This, although responsive to chemotherapy, makes small-cell lung cancer one of the most difficult cancers to treat. The prognosis for this kind of cancer varies from person to person and may be influenced by the person's overall health and the stage of the cancer at the time of diagnosis.
Causes of Lung Cancer
Majority of lung cancer is caused by smoking and as with any cancer, each person's genetic pattern influences susceptibility. Some families are more prone to get lung cancer through certain inherited genetic traits that make family members more susceptible than others to cancer-causing substances like those found in tobacco smoke.
Nevertheless, smokers who smoke one pack of cigarettes daily are 20 times more likely to develop lung cancer with the incidence almost tripling with two packs a day. Breaking the smoking habit reduces risk significantly, yet former smokers are always slightly more susceptible than non-smokers. Second hand tobacco smoke can also increase a person's susceptibility of developing lung cancer in comparison to others who live in a smoke free environment.
Lung tissue that has been scarred by disease or infection, such as scleroderma or tuberculosis, is more susceptible to tumour growth. Because of a high frequency of lung cancer among people who eat large amounts of fat and cholesterol, some researchers speculate that diet may also influence lung cancer risk.