Health A-Z

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What Is It?

Squamous cell carcinoma of the lung is a type of lung cancer. It occurs when abnormal lung cells multiply out of control and form a tumor. Eventually, tumor cells can spread (metastasize) to other parts of the body including the

  • lymph nodes around and between the lungs

  • liver

  • bones

  • adrenal glands

  • brain.

In general, there are two categories of lung cancer: small cell lung cancer and non-small cell lung cancer. The cancer cells in each type look different under the microscope. They are also treated differently. The prognosis for non-small cell lung cancer tends to be better than for small cell lung cancer; non-small cell lung cancers are more likely to be contained in one area, making treatment more likely to be successful.

Squamous cell carcinoma is one type of non-small cell lung cancer. The others are

  • adenocarcinoma

  • large cell carcinoma.

Adenocarcinoma is the most common type of lung cancer. Squamous cell carcinoma is the second-most common type. It accounts for about 30% of all cases of non-small cell lung caner.

Your risk of all types of lung cancer, including squamous cell carcinoma, increase if you

  • smoke. Smoking cigarettes is by far the leading risk factor for lung cancer. In fact, cigarette smokers are 13 times more likely to develop lung cancer than nonsmokers. Cigar and pipe smoking are almost as likely to cause lung cancer as cigarette smoking.

  • breathe tobacco smoke. Nonsmokers who inhale fumes from cigarette, cigar, and pipe smoking have an increased risk of lung cancer.

  • are exposed to radon gas. Radon is a colorless, odorless radioactive gas formed in the ground. It seeps into the lower floors of homes and other buildings and can contaminate drinking water. Radon exposure is the second leading cause of lung cancer. It's not clear whether elevated radon levels contribute to lung cancer in nonsmokers. But radon exposure does contribute to lung cancer in smokers and in people who regularly breathe high amounts of the gas at work (miners, for example). You can test radon levels in your home with a radon testing kit.

  • are exposed to asbestos. Asbestos is a mineral used in insulation, fireproofing materials, floor and ceiling tiles, automobile brake linings, and other products. People exposed to asbestos on the job (miners, construction workers, shipyard workers, and some auto mechanics) have a higher-than-normal risk of lung cancer. People who live or work in buildings with asbestos-containing materials that are deteriorating also have an increased risk of lung cancer. The risk is even higher in people who also smoke. Asbestos exposure also increases the risk of developing mesothelioma, a relatively rare and usually fatal cancer. It usually starts in the chest and resembles lung cancer.

  • are exposed to other cancer-causing agents at work. These include uranium, arsenic, vinyl chloride, nickel chromates, coal products, mustard gas, chloromethyl ethers, gasoline, and diesel exhaust.

Most cases of squamous cell carcinoma start in the center of the lungs. These tumors may cause some symptoms, such as coughing up blood, at an earlier stage than tumors on the edges of the lungs, such as adenocarcinomas.

Squamous cell carcinoma often spreads (metastasizes) to other parts of the body because of the constant flow of fluids (blood and lymph) through the lungs. The fluids can carry cancer cells to nearby areas, such as the chest wall, neck, esophagus, and the protective sac around the heart. Unless it is diagnosed and treated early, it often spreads throughout the body.

Many lung cancers have the ability to secrete chemicals that circulate in the bloodstream. These chemicals can change the way the body functions. Squamous cell lung cancer may secrete a substance that leads to abnormal calcium levels. This can cause kidney problems.

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From Health A-Z, Harvard Health Publications. Copyright 2007 by the President and Fellows of Harvard College. All rights reserved. Written permission is required to reproduce, in any manner, in whole or in part, the material contained herein. To make a reprint request, contact Harvard Health Publications. Used with permission of StayWell.

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