Lung cancer is the uncontrolled growth of abnormal cells in one or both of the lungs. While normal lung tissue cells reproduce and develop into healthy lung tissue, these abnormal cells reproduce rapidly and never grow into normal lung tissue. Lumps of cancer cells (tumors) then form and disrupt the lung, making it difficult to function properly.
More than 87% of lung cancers are smoking related. However, not all smokers develop lung cancer. Quitting smoking reduces an individual's risk significantly, although former smokers remain at greater risk for lung cancer than people who never smoked. Exposure to other carcinogens such as asbestos and radon gas also increases an individual's risk, especially when combined with cigarette or cigar smoking.
What Are The Types of Lung Cancer?
Non-small cell lung cancer accounts for about 80 percent of lung cancers. Among them are these types of tumors:
- Epidermold carcinoma (also called squamous cell carcinoma) forms in the lining of the bronchial tubes. This is the most prevalent type of lung cancer in men.
- Adenocarcinoma is found in the mucus glands of the lungs. This is the most common type of lung cancer in women and among people who have not smoked.
- Bronchioalveolar carcinoma, which is a rare subset of adenocarcinoma, forms near the lungs' air sacs. Recent clinical research has shown that this type of cancer responds more effectively to the newer targeted therapies.
- Large-cell undifferentiated carcinomas form near the surface (outer edges) of the lungs. They grow rapidly and often have spread by the time of diagnosis.
Small cell lung cancer accounts for 20 percent of all lung cancers. Although the cells are small, they multiply quickly and form large tumors that can spread throughout the body. Smoking is almost always the cause of small cell lung cancer.
How is Lung Cancer Diagnosed?
Early detection of lung cancer is critical to improving chances of survival. Physicians use a number of different tests to detect and diagnose lung cancer, including sophisticated imaging scans that provide more accurate and sensitive results than conventional X-rays. The information from these tests enables the physician to determine the type and stage of the cancer and the best way to treat it.
- Physical Examination: is important for detecting any signs of cancer such as swollen lymph nodes in the neck or collarbone area and also for evaluating overall state of health.
- Chest examination: examining the chest and listening to the lungs with a stethoscope provides information about abnormal breathing sounds or patterns.
- Chest X-ray: are "flat" pictures of the lungs, which help to identify abnormal growths.
- CT scan: computed tomography also known as a CAT scan is a sophisticated instrument that uses a computer to create a two-dimensional scan from a series of X-ray images; the newest version of the CT is called a helical (or spiral) scan. CT scans reveal much more detail than x-rays and the new helical scans are even more sensitive than regular CT scans.
- PET scan: positron emission tomography is a scan that traces the way the body cells act on sugar. PET scans can find cancerous tumors because of their ability to take up radioactive sugar.
- MRI: magnetic resonance imaging is similar to a CT scan except it uses a magnetic field in place of X-rays to create an image.
- Sputum cytology: coughed-up phlegm from the lungs is examined under a microscope to check for abnormal or cancerous cells.
- Bronchoscopy: viewing of the lungs through a hollow, flexible tube (bronchoscope) that is passed through the nose and throat into the main airway of the lungs. If abnormal areas or tumors are seen, biopsies can be obtained through the bronchoscope.
- Biopsy: removal of a lung tissue sample for examination under a microscope. Biopsies are obtained in different ways depending on the location of the tumor:
- through a bronchoscopy
- by inserting a needle through the chest into the lung
- by removal and examination of an enlarged lymph node in the neck
- by a small surgery on the lung
The newer imaging scans (CT, PET and MRI) are very sensitive and can reveal cancerous growths not seen by conventional chest X-rays. Clinical trials are underway to determine the effectiveness of screening to permit the early detection of lung cancer based on these new advances.
Small Cell Lung Cancer
- Limited: Tumor is found in one lung and in nearby lymph nodes.
- Extensive: Tumor has spread beyond one lung or to other organs.
Non-Small Cell Lung Cancer
- Stage I a/b: Tumor of any size is found only in the lung.
- Stage II a/b: Tumor has spread to lymph nodes associated with the lung.
- Stage III a: Tumor has spread to the lymph nodes in the tracheal area, including chest wall and diaphragm.
- Stage III b: Tumor has spread to the lymph nodes on the opposite lung or in the neck.
- Stage IV: Tumor has spread beyond the chest.