Definition

• A carcinoma is defined as a cancerous growth arising from epithelial cells in the body, and is most commonly found in the lungs (due in large part to the carcinogenic effect of smoking), although it can affect other organ systems and the skin. Along with smoking, it can be caused by exposure to the sun (in skin carcinomas), exposure to carcinogenic chemicals such as benzene, specific viruses, sunlight and radiation.
  
  

Adenocarcinoma

• Adenocarcinoma develops in the cells lining certain internal organs (glandular types) such as the lungs, the breast, colon, prostate, pancreas,and cervix, but it is most common in the lungs. Abnormal epithelial cells start to multiply uncontrollably, creating a tumor in the lungs. Sometimes, the tumor cells metastasize, spreading to other parts of the body. This form of carcinoma is commonly found in smokers, and is the most common form of lung cancer.
  
  

Small-Cell Carcinoma

• As with adenocarcinoma, small-cell carcinoma most commonly affects the lungs, but can also affect the cervix, prostate or other organs. It is most commonly found in smokers, and is often extremely malignant. It is generally divided into two stages: limited and extensive. If in limited stage, small-cell carcinoma has not yet metastasized and remains in its area of origin. In extensive stage small-cell carcinoma, the cancer has metastasized beyond the point of origin. It can be treated, but the prognosis is not as good as with other forms of cancer.
  
  

Large-Cell Carcinoma

• Large-cell carcinomas occur most typically in the lungs, like other carcinomas, and result from uncontrolled cell growth in the epithelial cells of the affected organ. As with other carcinomas, it is also often associated with smoking. It has a tendency to grow quickly and metastasize early, sometimes secreting chemicals into the blood that cause several adverse reactions, including gynecomastia, or breast tissue growth in men.
  
  

Squamous Cell Carcinoma

• Squamous cell carcinoma is the second-most common form of skin cancer and is most commonly caused by uncontrolled cell growth as a result of exposure to the sun's harmful UV rays. It is usually caught early, as it is relatively easy to identify and apparent on the skin from an early stage. Unlike many other, more invasive cancers, squamous cell carcinoma is generally treated with surgical excision, laser therapy or freezing, although radiation or chemotherapy can be used in places where surgery isn't practical. If left untreated, it can spread to other parts of the body.