What is lung cancer?
Lung cancer is a disease in which abnormal cells appear in the lung and start to multiply rapidly and uncontrollably. Usually it happens as a result of a genetic mutation or prolonged exposure to certain risk factors such as tobacco smoke, asbestos or air pollutants. The abnormal cells form a lump called a tumor. Cancerous tumors, otherwise called malignant tumors, have the potential to spread into nearby tissue replacing normal cells. Also, cancer cells can separate from the tumor in the lung and travel through the bloodstream or lymph vessels to other tissues and organs of the body, most often to lymph nodes, bones, liver, brain or adrenal glands. Such a cell-traveler is called metastasis.
The precise location of the tumor in the lung and its speed of growth vary in different types of lung cancer.
What are the types of lung cancer?
There are two main kinds of lung cancer which differ from each other in the type of cells affected. Non-small cell lung cancer accounts for 85% of all cases. It is an umbrella term for several types of lung cancers. It may begin in the outer part of the lungs from mucus-producing cells that form part of the lining of the lungs, in larger airways from thin flat cells, or be an undifferentiated carcinoma in which the cells are very immature and do not look like cells in the tissue of the lung. It is known that an undifferentiated cancer is more malignant.
Small cell lung cancer, previously known as oat cell carcinoma, makes up the rest 15%. It tends to start in the middle of the lungs and generally spreads more quickly. It occurs almost exclusively in heavy smokers.