lung cancer

Lung cancer
The environmental disease, lung cancer, is the uncontrolled growth of abnormal cells in one or both lungs. These cancerous cells are generally caused by mutations in the normal cells from exposure to carcinogens, or cancer-causing agents. Normal cells in the body are renewed and multiply by mitosis. The cells replace the old cells and continue to function normally. However, abnormal calls grow and replicate but do not act and function as the normal lung tissue. Over time, these abnormal cells turn into lumps (tumours). In a benign tumour the cells do not spread to other parts of the body and so are not cancerous. If they continue to grow at the original site, however, they may cause a problem by pressing on the surrounding organs. A malignant tumour consists of cancer cells that have the ability to spread beyond the original site. If the tumour is left untreated, it may invade and destroy surrounding tissue. Sometimes cells break away from the original (primary) cancer and...