Small cell lung cancer is a disease in which malignant (cancer) cells form in the tissues of the lung.

The lungs are a pair of cone-shaped breathing organs that are found within the chest. The lungs bring oxygen into the body when breathing in and take out carbon dioxide when breathing out. Each lung has sections called lobes. The left lung has two lobes. The right lung, which is slightly larger, has three. A thin membrane called the pleura surrounds the lungs. Two tubes called bronchi lead from the trachea (windpipe) to the right and left lungs. The bronchi are sometimes also involved in lung cancer. Small tubes called bronchioles and tiny air sacs called alveoli make up the inside of the lungs.

Anatomy of the respiratory system, showing the trachea and both lungs and their lobes and airways. Lymph nodes and the diaphragm are also shown. Oxygen is inhaled into the lungs and passes through the thin membranes of the alveoli and into the bloodstream (see inset).

There are two types of lung cancer: small cell lung cancer and non-small cell lung cancer. This summary provides information on small cell lung cancer. (Refer to the PDQ summary on Non-Small Cell Lung Cancer Treatment for more information.)

There are three types of small cell lung cancer.

These three types include many different types of cells. The cancer cells of each type grow and spread in different ways. The types of small cell lung cancer are named for the kinds of cells found in the cancer and how the cells look when viewed under a microscope:

• Small cell carcinoma (oat cell cancer).
• Mixed small cell/large cell carcinoma.
• Combined small cell carcinoma.

Smoking tobacco is the major risk factor for developing small cell lung cancer.

Cigarette smoking is the most common cause of lung cancer. Risk factors for small cell lung cancer include:

• Smoking cigarettes, cigars, or pipes now or in the past.
• Being exposed to second hand smoke.
• Being exposed to asbestos or radon.

Possible signs of small cell lung cancer include coughing, chest pain, and shortness of breath.

These and other symptoms may be caused by small cell lung cancer or by other conditions. A doctor should be consulted if any of the following problems occur:

• A cough that doesn’t go away.
• Shortness of breath.
• Chest pain that doesn’t go away.
• Wheezing.
• Coughing up blood.
• Hoarseness.
• Swelling of the face and neck.
• Loss of appetite.
• Unexplained weight loss.
• Unusual tiredness.

Tests and procedures that examine the lungs are used to detect (find) and diagnose small cell lung cancer.

The following tests and procedures may be used:

• Chest x-ray: An x-ray of the organs and bones inside the chest. An x-ray is a type of energy beam that can go through the body and onto film, making a picture of areas inside the body.

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What causes pancreatic cancer?

What causes pancreatic cancer?

While it is virtually impossible to tell what caused a specific person to develop pancreatic cancer, there are some important principles of cancer biology that can help us understand why pancreatic cancer develops, and large population-based studies help us understand the many risk factors for this disease.

Pancreatic cancer is fundamentally a disease caused by damage to the DNA (mutations). These mutations can be inherited from mom or dad, or they can be acquired as we age. First, let us look at the inherited mutations. Remember that we have two copies of each gene - one copy we inherit from mom, the other copy we inherit from dad. Most individuals with an inherited cancer syndrome inherit one mutant copy (let us say from dad) and one intact (normal) copy (let us say from mom) of a cancer associated gene. As they age, some of these people will damage the good copy of the gene (the copy they got from mom) in a cell in their pancreas. That cell will have two bad copies of the gene, and, as a result, that cell in the pancreas will grow into a cancer. It doesn’t mean that everyone with an inherited predisposition will get cancer, it means that since they only have one copy of the gene, they are more likely to get cancer. I like to think of it using the analogy of the space shuttle, with the shuttle standing in for a person, and computers on the space shuttle standing in for genes. Normally the shuttle goes into space with a computer and a back-up for that computer. Only if both computers break is there a problem. For people with a genetic predisposition to pancreatic cancer, it is like going up into space with one good computer and one bad computer. If something goes wrong with the one good computer, they are in trouble.

The second way we can damage our DNA is with our behavior. The carcinogens in cigarette smoke can damage our DNA. If the carcinogens damage a key cancer-associated gene in a cell in the pancreas, then that cell may grow into a cancer. Simply put, don’t smoke! The third way our DNA gets damaged is by chance. This is probably the least satisfying explanation, but it is true. Every cell in our body (and there are trillions of them!) contains a 23 chromosomes and these 23 chromosomes contain 3 billion base-pairs of DNA. Every time a cell divides it has to copy all of that DNA (so that it can make a daughter cell with a full complement of DNA). The DNA copying machinery in cells is pretty darn good, but it is not perfect. Occasionally mistakes are made. On one hand, this is good from a population or species perspective, because these mistakes allow for evolution to occur (if we copied our DNA perfectly we would not evolve!). If one of these chance errors in copying (DNA mutations) damage a key cancer-associated gene in a cell in the pancreas, then that cell may grow into a cancer.

 

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Causes of acute cholecystitis

Causes of acute cholecystitis 

Illustration of the gallbladder, liver, bile duct and stomach

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