Primary lung cancer is the uncontrolled proliferation of malignant cells in the airways and air sacs of the lungs. Lung cancer is an aggressive cancer that can spread to other parts of the body.Lung cancer is of two basic types – non-small cell and small cell lung cancer . Of these the non small cell lung cancer accounts for a majority of cases of lung cancer. it grows and spreads more slowly than small cell cancer. The small cell lung cancer grows and spreads very rapidly to other parts of the body.
Tumors can be benign or malignant; when we speak of "cancer," we refer to those tumors that are considered malignant. Benign tumors can usually be removed and do not spread to other parts of the body. Malignant tumors, on the other hand, grow aggressively and invade other tissues of the body, allowing entry of tumor cells into the bloodstream or lymphatic system and then to other sites in the body. This process of spread is termed metastasis; the areas of tumor growth at these distant sites are called metastases. Since lung cancer tends to spread or metastasize very early in its course, it is a very life-threatening cancer and one of the most difficult cancers to treat. While lung cancer can spread to any organ in the body, certain organs particularly the adrenal glands, liver, brain, and bone -- are the most common sites for lung-cancer metastasis.

The exact cause of lung cancer is not determined. But there are certain risk factors that predispose an individual to lung cancer. Some of them are:

The doctor examines the chest area with a stethoscope in which a persistent wheezing sound acts as an alarm. Localized wheezing may be noticed, which is the low almost musical sound emitted when there is partial blockage in the air passages of the lungs. A chest X-ray is usually advised, which can show the cancerous lesions in the lungs. Sometimes, fluid may accumulated in the chest, and a sample of the fluid from the lungs may be taken for testing. A needle is inserted through the chest wall and some of the fluid is extracted. A sample of the sputum may also be taken to check for malignant cells.Bronchoscopy is a procedure in which a thin lighted tube, called the bronchoscope, is passed through the mouth, via the wind pipe (trachea) into the lungs to examine the inside of the air passages. If a lesion is seen in chest X-ray or bronchoscopy, a small amount of the lung tissue is taken or biopsied for laboratory testing.

Since lung cancer tends to spread throughout the body, chemotherapy is the most common form of treatment. Chemotherapy drugs include doxorubicin or adriamycin, vincristine,and etoposide. Radiation therapy may be used if the exact area of the origin of the tumour is located. In some cases, surgery of the lungs may have to be carried out. The procedure involves the removal of only the tumour, a lobe of the lungs or the whole lung, depending on the location of the tumour and the extent of damage. Lung surgery is a major operation and the patient may need to be in hospital for several days following surgery. The patient must breathe deeply and frequently to expand the lung tissue which aids in recovery.