Lung cancer often takes many years to develop. First, there may be areas of pre-cancerous changes in the lung. These changes are not a mass or tumor. They can’t be seen on an x-ray and they don’t cause symptoms.
Over time, these pre-cancerous areas can become cancer. The cancer makes chemicals that cause new blood vessels to form nearby. These new blood vessels feed the cancer cells and allow a tumor to form. In time, the tumor becomes large enough to show up on an X-ray.
The pathologist checks the sputum, pleural fluid, tissue or other samples for cancer cells. Most lung cancer starts in the lining of the bronchi, but it can also start in other parts of the lung.
There are different types of lung cancer and each is treated differently. The two most common types are named for how the lung cancer cells look under a microscope:
Small Cell Lung Cancer
Small cell lung cancers tend to spread quickly. People with limited stage small cell lung cancer usually have radiation therapy and chemotherapy. For a very small lung tumor, a person may have surgery and chemotherapy. Most people with extensive stage small cell lung cancer are treated with chemotherapy only. About 13 percent of lung cancers are small cell lung cancer.
Non-Small Cell Lung Cancer
Non-small cell lung cancer spreads more slowly than small cell lung cancer. People with non-small cell lung cancer may have surgery, chemotherapy, radiation therapy or a combination of treatments. The treatment choices are different for each stage. Some people with advanced cancer receive targeted therapy. About 87 percent of lung cancers are non-small cell lung cancers.
How Lung Cancer Spreads
At some point, cancer cells can break away and spread to other parts of the body in a process called metastasis. Lung cancer is a life-threatening disease because it often spreads before it is found.
One of the ways lung cancer can spread is through the lymph system. Lymph vessels are like veins, but they carry lymph fluid instead of blood. Lymph is clear fluid that contains tissue waste products and cells that fight infection. Lung cancer cells can enter lymph vessels and begin to grow in lymph nodes around the bronchi and in the area between the lungs.
When lung cancer cells have reached the lymph nodes, they are more likely to have spread to other organs of the body. Staging and decisions about lung cancer treatment are based on whether or not the cancer has spread to the nearby lymph nodes.
Diagnosing & Staging
When cancer spreads from its original place to another part of the body, the new tumor has the same kind of cancer cells and the same name as the original cancer. For example, if lung cancer spreads to the liver, the cancer cells in the liver are actually lung cancer cells. The disease is metastatic lung cancer, not liver cancer. For that reason, it's treated as lung cancer, not liver cancer. Doctors call the new tumor "distant" or metastatic disease. Staging lung cancer may involve blood tests and other tests:
CT scans may show cancer that has spread to the liver, adrenal glands, brain, or other organs. A patient may receive contrast material by mouth and by injection into the arm or hand. The contrast material helps these tissues show up more clearly. If a tumor shows up on the CT scan, the doctor may order a biopsy to look for lung cancer cells.
A bone scan may show cancer that has spread to the bones. The patient receives an injection of a small amount of a radioactive substance. It travels through the blood and collects in the bones. A machine called a scanner detects and measures the radiation. The scanner makes pictures of the bones on a computer screen or on film.
A doctor may order MRI pictures of the brain, bones or other tissues. MRI uses a powerful magnet linked to a computer. It makes detailed pictures of tissue on a computer screen or film.
Doctors use a PET scan to find cancer that has spread. The patient receives an injection of a small amount of radioactive sugar. A machine makes computerized pictures of the sugar being used by cells in the body. Cancer cells use sugar faster than normal cells and areas with cancer look brighter on the pictures.
Bronchoscopy is a technique of visualizing the inside of the airways for diagnostic and therapeutic purposes. An instrument (bronchoscope) is inserted into the airways, usually through the nose or mouth. Endobronchial Ultrasound (EBUS) allows physicians to use ultrasound devices inside the airways and the lung for exploration of the structures of airway walls, the surrounding mediastinum and the lungs.