There are two types of lung cancer, in which tumors originate in the lungs, as opposed to having migrated from elsewhere in the body. These are non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC). Physicians make a diagnosis based on the appearance of cancer cells under a microscope and the way the cancer behaves. Different types of lung cancer respond to treatment differently and according to their stage, so it is crucial to identify the exact type.
Non-small cell lung cancer (NSCLC)
Most lung cancers are diagnosed as NSCLC, making up around 80 to 85 percent of tumors. This term covers multiple similar lung cancers that develop in different locations in the lung but behave similarly. NSCLC is further divided into three types: adenocarcinoma, squamous cell carcinoma or large cell carcinoma. However, it is possible for multiple types of NSCLC cells to be identified in a single tumor. If the cancer is in its very early stages, it can be difficult to accurately identify the type, and the cancer may be diagnosed as “undifferentiated NSCLC” until a more accurate diagnosis can be made.
Adenocarcinoma is the most common form, accounting for about 40 percent of diagnoses. Adenocarcinomas are also the most common type seen in non-smokers. It is more common in women than men and in younger people. It develops in the mucus-making glands in the lining of the airways and tends to progress more slowly than other types.
Squamous cell carcinoma
Squamous cell carcinoma develops in the center of the lung, typically starting in the flat “squamous” cells that line the airways. Smoking can cause this type of cancer.
Large cell carcinoma
Large cell carcinomas are defined by the size of cancer cells under a microscope. If cancer develops in the hormone-releasing cells of the lungs, it is called a large cell neuroendocrine cancer (LCNEC). This type is one of the fastest-growing lung cancers. Hormones act as chemical messengers, delivering signals to other organs and areas of the body, and their incorrect regulation causes a variety of other problems.
Other types of NSCLC can occur (including adenosquamous carcinoma and sarcomatoid carcinoma), but these are very rare.
Small cell lung cancer (SCLC)
This type of lung cancer is less common (around 10 to 15 percent of diagnoses), and it occurs almost exclusively in heavy smokers. SCLC usually grows faster than NSCLC and can spread quickly.
Rarer types of lung cancer
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