Lung cancer is a type of cancer that starts in the lungs. Cancer starts when cells in the body begin to grow out of control. It is the leading cancer in world which accounts 2.1 million in terms of new cases in 2018.

There are two main types of lung cancer: non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC). NSCLC is the most common type of lung cancer. In fact, about 80%-85% of lung cancer cases are NSCLC.

Adenocarcinomas start in the cells that would normally secrete substances such as mucus. This type of lung cancer occurs mainly in current or former smokers, but it is also the most common type of lung cancer seen in non-smokers. It is more common in women than in men, and it is more likely to occur in younger people than other types of lung cancer. Adenocarcinoma is usually found in the outer parts of the lung and is more likely to be found before it has spread. People with a type of adenocarcinoma called adenocarcinoma in situ (previously called bronchioloalveolar carcinoma) tend to have a better outlook than those with other types of lung cancer.

Squamous cell carcinomas start in squamous cells, which are flat cells that line the inside of the airways in the lungs. They are often linked to a history of smoking and tend to be found in the central part of the lungs, near a main airway (bronchus).

arge cell carcinoma can appear in any part of the lung. It tends to grow and spread quickly, which can make it harder to treat. A subtype of large cell carcinoma, known as large cell neuroendocrine carcinoma, is a fast-growing cancer that is very similar to small cell lung cancer.

If your cancer cells look very undeveloped under the microscope, your doctor won’t be able to tell which type of NSCLC you have. Undeveloped cancer cells are called undifferentiated cancers. So, your doctor might say you have undifferentiated NSCLC.

About 10% to 15% of all lung cancers are SCLC and it is sometimes called oat cell cancer. This type of lung cancer tends to grow and spread faster than NSCLC. About 70% of people with SCLC will have cancer that has already spread at the time they are diagnosed. Since this cancer grows quickly, it tends to respond well to chemotherapy and radiation therapy. Unfortunately, for most people, the cancer will return at some point.