Types of lung cancer

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

Non-small cell lung cancer

There are three main types:

  • Adenocarcinoma is the most common type of lung cancer. It develops from mucus-producing cells that line the airways.
  • Squamous cell carcinoma develops in the cells that line the airways. It is usually caused by smoking.
  • Large cell carcinoma (sometimes called undifferentiated carcinoma) is named because of how the cancer cells look when examined under a microscope.

Small cell lung cancer

Small cell lung cancer (SCLC) also gets its name from how the cancer cells look when examined under a microscope. It’s usually caused by smoking, and very rarely develops in someone who has never smoked. SCLC usually grows quickly and can spread quickly.


This is a cancer of the covering of the lungs (the pleura) and is less common. We have separate information about mesothelioma.

Rarer types of lung cancer

Some people get other rarer types of lung cancer. Carcinoid tumours are rare cancers that sometimes develop in the lungs.

Back to Understanding non-small cell lung cancer

The lungs

When we breathe the lungs take oxygen into the bloodstream and remove carbon dioxide.

What is cancer?

Cancer is a disease of our cells. Sometimes cells go wrong and become abnormal. They keep dividing to make more abnormal cells which form a lump or tumour.

Why do cancers come back?

Sometimes, cancer cells are left behind after cancer treatment. Over time, these cells can form a new tumour and the cancer comes back.