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Lung Basics

The human lung is one of the largest organs in the human body. Breathing--and life itself--is impossible if your lungs aren't working.

During a normal day, your lungs breathe in and out nearly 25,000 times. People with lung disease have difficulty breathing.

The lungs occupy a large percentage of the chest cavity, and each lung is protected by the rib cage. The lungs vary slightly in size: the left lung is a little bigger than the right lung because it shares more space with the heart. The diaphragm, which is located just below the lungs, expands and contracts to push carbon dioxide out of each lung and draw fresh oxygen in.

The lungs also make it possible for us to communicate through speech.

Lung Function

Here's how the lungs work.
Air comes into the lungs through the windpipe into two tubes called bronchi, which are part of the respiratory system. The bronchi then divide into bronchioles, which are smaller tubes. The bronchioles divide even further into tiny air sacs called alveoli.

On the inside, a normal lung is pinkish in color, and it resembles a sponge with many tiny holes and bubbles. Minute blood vessels surround these holes, and the blood vessels exchange carbon dioxide for oxygen. This is known as "gas exchange." Blood that has circulated throughout the body is pumped by the heart each lung. After the gas exchange, the blood goes from the lung back to the heart where it is pumped to the rest of the body. This process is called pulmonary circulation. Without oxygen from our lungs, our cells could not function.


The lungs are a primary site for breast cancer spread, second to the bones. Studies show that first metastases go to the lungs in approximately 19 percent of cases.

When cells break away from a cancerous tumor (a primary tumor) they can travel to other parts of the body through the bloodstream or the lymph vessels. Moving through the bloodstream or lymphatic system, cancer cells can lodge in an organ at a distant location and establish a new (secondary) tumor.

Secondary tumors that have spread to lung (lung mets) through the process known as lung metastasis are not the same as primary lung cancer that starts in the lungs (sarcoma). A tumor that has metastasized to lung is made up of abnormal cancer cells from the original tumor site and not of lung cells. Breast cancer that spreads to the lung consists of breast cancer cells. In this case, lung metastasis would be called metastatic breast cancer.

Symptoms of Lung Metastases

Symptoms of lung metastases vary. Some patients are diagnosed on a routine checkup, but most do have symptoms. These may include a persistent dry cough not associated with other health issues, unexplained shortness of breath, or a dull pain in the back or side. Common symptoms of lung cancer are caused by the growth of the tumor in the lung. Other symptoms, such as weight loss, fatigue, and loss of appetite, are suggestive of cancer in general.

  • Cough
  • Hemoptysis
  • Dyspnea
  • Wheezing
  • Chest, shoulder, or arm pain
  • Weight loss
  • Fatigue
  • Loss of appetite


Chest X-ray
Chest radiography (x-ray) is used to create an image of the organs and bones inside the chest. X-rays pass through the body and onto film, creating a photographic image. Although radiography is especially effective at detecting bony structures, images generated this way can also reveal abnormalities in other tissues, such as scarring and tumors in the lungs.

CT Scan
CT scanning is a procedure that uses x-rays to make a series of detailed images of the inside of the body, taken from different angles. This procedure is also called computerized tomography or computerized axial tomography. A contrast-enhancing dye may be injected into a vein or swallowed to make organs or tissues show up more clearly. Final images of cross-sections of the body are made by computer processing of the actual x-ray images.

MRI Scan
In magnetic resonance imaging (MRI), radio waves and a powerful magnet linked to a computer are used to create detailed images of areas inside the body. MRI provides better images of organs and soft tissue than other scanning techniques, such as CT or radiography. In lung cancer staging, MRI is used most often to detect brain metastases.

PET Scan
A positron emission tomography (PET) scan is an imaging procedure used to visualize malignant tumor cells in the body. A small quantity of radiolabeled glucose is injected into a vein. The PET scanner rotates around the body and creates computer-generated images of where glucose is being used in the body.

In images generated by PET scanning, malignant tumor cells appear brighter than the surrounding normal tissues because they are more metabolically active and take up more glucose than do normal cells. In lung cancer staging, PET is used to detect lymph node and distant metastases.


In most cases, metastatic cancer to the lung is a sign that the cancer has spread into the bloodstream. Usually cancer will be present even in places not seen by CT scans. In these circumstances, removing the visible tumors with surgery is usually not beneficial. Chemotherapy is usually the treatment of choice. Sometimes when the primary tumor has been removed and the cancer has spread to only limited areas of the lung, the lung tumors can be removed with surgery. However, the main tumor must be curable, the lung tumors must be able to be completely cut out, and the patient must be strong enough to go through the surgery and recovery.

Other, less common treatments include:

  • Radiation therapy
  • The placement of stents inside the airways
  • Laser therapy

There are other experimental treatments. One of these treatments uses local heat probes to destroy the area. Another drips chemotherapy directly into the artery that supplies blood to the part of the lung containing the tumor.

Last Updated on Thursday, 21 January 2010 10:16