There are two main types of primary lung cancer. They behave differently and respond to treatment in different ways. These are:

* non-small cell lung cancer (NSCLC), the most common type.

* small-cell lung cancer (SCLC), which accounts for about 10% of all cases of lung cancer.

Non-small cell lung cancer
There are three main types:

• Squamous-cell carcinoma
  This is the most common type and develops in cells that line the airway. It is usually caused by smoking.

• Adenocarcinoma
  This develops from mucus-producing cells located in the airway. This type is becoming more and more common.

• Large-cell carcinoma
  Sometimes called undifferentiated carcinoma, it owes its name to the appearance of the cancer cells when they are examined under a microscope.

Small-cell lung cancer (SCLC)
This type of cancer gets it name from the way the cells look when they are examined under a microscope. It is usually caused by smoking and is rare in people who have never smoked. SCLC normally grows and spreads quickly.

Mesothelioma
This is a cancer of the lining of the lungs (pleura) and is less common.

Rarer types of lung cancer
Some people have other, less common types of lung cancer.
Carcinoid tumors or soft-tissue sarcomas are infrequently seen cancers that sometimes develop in the lungs.