Small cell cancer of the lung comprises one of the major cell types of cancers of the lung. Conceptually, lung cancers can be categorized as small cell cancers or so called non-small cell cancers. The major types of the non-small cell variety include squamous cancer, large cell cancer of the lung, and adenocarcinoma.

The distinction between small cell and non-small cell cancer is important, since prognosis, staging and treatment programs are in large part dictated by the specific type of cancer that is present. While most small cell cancers arise in the lung, they may arise in other organs, independent of the lung. This includes small cell cancers of the bowel, bladder, prostate, and rarely, other organs. Unfortunately, small cell cancers arising from the lung and other sites behave in a very aggressive fashion and generally carry a poor prognosis.

One of the important reasons for distinguishing a small cell cancer of the lung from non-small cell varieties relates to the likelihood of the cancer being contained when first discovered. Small cell cancers rarely stay confined to one area, even when the initial evaluation shows no spread.

More often, at the time of diagnosis, the small cell lung cancer has spread or metastasized widely throughout the body. This is true, even if the staging studies that assess the extent of the cancer are normal or negative. Usually, small cell cancer of the lung has spread widely at the first time of detection and cannot be cured by surgical removal of the lung. This is the main reason why patients with small cell cancers are not offered surgery to remove the lung after the diagnosis. Rather, they are treated with chemotherapy or radiation, or both, and not surgery.

Small cell lung cancer has been called oat cell cancer because the cells resemble oats when seen under a microscope. This cancer usually originates in the lung's large central airways (the bronchi). It accounts for about 20% of all lung cancers. In some cases, small cell tumors also include cells that have non-small cell features. This condition is called a mixed tumor.

All types of lung cancer are associated strongly with smoking. About 90% of people who get small cell lung cancer are either current or past smokers. Small cell cancers possess the ability to secrete various chemical substances and hormones that have actions independent of the actual cancer. When a cancer behaves this way, doctors call it a paraneoplastic disorder or paraneoplastic phenomenon. Sometimes the diagnostic possibility of small cell cancer of the lung is suggested by symptoms related to the extra production of a hormone. For example, small cell tumor cells may secrete adrenocorticotropic hormone, causing Cushing's disease, which might cause a puffy face, weight gain, hump on the lower neck, or elevated blood sugar levels. Tumors may secrete antidiuretic hormone, leading to water retention and low sodium, which causes confusion. Small cell cancer also produces antibodies that cause a specific type of weakness.

Abnormalities of some of the minerals in the body can also occur with small cell cancers of the lung. In addition, small cell tumors also may have the ability to secrete group of chemical substances that have so-called neuroendocrine activity � cells that cause abnormalities of the nervous system. These neuroendocrine chemicals can be measured and looked for by using special tissue stains in the pathology laboratory or by measuring the blood for the presence of specialized chemicals.

Because small cell cancer of the lung can arise in the central portion of the chest and in close proximity of the great blood vessels of the chest, such as the large vein (superior vena cava) in the upper part of the chest, it is not uncommon for this large vein to become blocked due to growth of the small cell cancer. When this occurs, the blood from the head and brain area will be blocked as it tries to empty itself. This causes a back up of the blood. Patients may experience headache, a red face, a bloated appearance of the head, and bulging veins in the front part of the chest and neck. When this occurs, it is called superior vena cava syndrome and represents a medical emergency. The diagnosis of small cell cancer needs to be quickly confirmed by biopsy, so that treatment with chemotherapy or radiation therapy, or both, can begin immediately.

Small cell lung cancer is among the fastest growing cancers. In the vast majority of (nearly all) people with this cancer, the cancer already has spread (metastasized) by the time of diagnosis. The cancer can spread easily because of the constant flow of fluids through the lungs. These fluids consist of blood and lymph (a protein-filled fluid from the lymphatic system). The fluids can carry cancer cells to lymph nodes, the heart, the other lung, and organs outside of the chest. Small cell lung cancers spread to any area of the body. It most commonly spreads to the brain, liver, adrenal glands, and bone.

Although some cancers do not have any symptoms at first, others are diagnosed during an evaluation for any of the following:

• A persistent cough
• Coughing up blood (hemoptysis)
• Shortness of breath or wheezing
• Unexplained weight loss or loss of appetite
• Fatigue
• Difficulty swallowing
• Pain in the chest, shoulder or arm
• Bone pain
• Hoarseness
• Headaches, confusion or seizures
• Swelling of the face, neck or upper extremities
• Prominent or bulging veins over the surface of the chest and neck

Lung cancer often is discovered on a chest X-ray, where it appears as a gray or whitish area. Other imaging studies, such as computed tomography (CT), magnetic resonance imaging (MRI), and PET scanning can further determine the size, shape and location of the tumor and locate areas where the tumor has spread. This helps to find the best place to obtain a sample of the tumor to diagnose small cell versus other types of lung cancer, such as squamous cell, large cell or adenocarcinoma of the lung. The type of cancer determines the treatment.

Small cell lung cancer sometimes can be diagnosed with a technique called sputum cytology, in which mucus from the lungs (sputum) is examined under a microscope to check for abnormal cells. Cancer cells also can be found in the fluid between the lung and the chest wall (requiring a procedure that uses a needle to remove fluid) or in lymph nodes next to the lung (requiring a surgical procedure).

Another diagnostic technique is needle aspiration, in which fluid or tissue is removed (aspirated) from lymph nodes or suspicious masses. Cells also can be removed during bronchoscopy. A fiberoptic viewing tube is inserted into the lung through the mouth and bronchial tubes. It allows the doctor to examine the tumor directly and to remove cells for examination.

In addition to the above tests, you may need a bone scan, bone marrow biopsy, CT or MRI scan of the head and brain, and additional biopsies to determine the degree of tumor spread. The reason for performing the tests of the head and brain reflects the likelihood that small cell cancers commonly spread to this area. These tests help establish the diagnosis even in the absence of symptoms. Small cell lung cancer has two stages:

• Limited cancer is confined to one lung and nearby lymph nodes.
• Extensive cancer has spread to both sides of the chest or beyond the chest.

The reason for making this staging distinction can help determine whether to offer radiation therapy (in addition to chemotherapy) that will encompass the lung area involved with the limited stage cancer.

As with any cancer, even if small cell cancer disappears (goes into remission), there is a chance it can come back.

Quit smoking and avoid secondhand smoke. Tobacco smoke is the main risk factor for small cell lung cancer. Although studies are trying to create reliable screening tests to diagnose lung cancer earlier, no test has been proven effective. Even though a recent study that used a very sophisticated type of chest CT scan as a screening test detected "earlier" stages of lung cancer, there was no overall benefit in terms of an increase in survival for patients who underwent screening. Again, this type of finding underscores that many lung cancers, especially small cell lung cancers, are widely metastatic at the time of early diagnosis.

Surgery rarely is done when small cell lung cancer is diagnosed because the cancer grows quickly and usually has already spread to many lymph nodes or beyond the lung and thus cannot be cured by surgical removal. Patients are often confused when surgical removal of the lung is not offered after being diagnosed. This is because the cancer cells have spread beyond the limits of the surgery. In other words, surgery is offered when the physician feels that all of the cancer can be removed and can result in a cure of the patient.

Small cell lung cancer cells are present in areas that will not and cannot be removed by surgery even if all the scans look OK. This cancer grows very rapidly, so surgery is not the main part of treatment. Chemotherapy (with or without radiation) is the main therapy. This is in contrast to non-small cell cancer, where surgical removal of the lobe of the lung or the lung itself is commonly offered as the main treatment.

The specific treatment depends on the stage or degree of cancer spread. The earlier stage allows for more intense and effective radiation therapy within a small area.

For the best chances of remission, radiation therapy typically is combined with chemotherapy, in alternating cycles. If a person has many other serious medical problems or cannot tolerate high-dose radiation or chemotherapy, he or she may be given altered doses to relieve specific symptoms such as bone pain. If tests show cancer remission at 6 to 12 weeks, some doctors will advise radiation to the brain to eliminate microscopic cancer cells that may be too small to see on CT scan or MRI.

In people with extensive-stage cancer, radiation usually isn't used except to relieve specific symptoms, such as bone pain, that are caused by the spread of the tumor.

In extremely rare and highly unusual cases, if the tumor has not spread to nearby lymph nodes, surgery is done to remove the tumor. This is more likely if the tumor is located at the edges of the lung instead of the more common central location. The chance for cure and prolonged survival is greater if surgery can be done, especially if chemotherapy is used as well.

If you experience any symptoms of small cell lung cancer, make an appointment to see your health care professional as soon as possible.

Because small cell lung cancer grows and spreads so rapidly, the prognosis is poor. The 5-year survival rate is about 6%. The survival rate is higher when the disease is diagnosed and treated at the earlier, limited stage.

Even when treatment is successful initially, there is a high risk that the cancer will come back, often at a location different from where it was first seen.

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