Small cell lung cancer and non-small cell lung cancer are the two main groups of primary lung cancer.
Small cell lung cancer
Small cell lung cancer is sometimes called oat cell cancer. Under a microscope, the cancer cells look small and filled by the nucleus, which is where it gets its name. Around three out of twenty-five lung cancer cases are small cell lung cancer.5 It’s often caused by smoking. It’s unusual for someone who’s never smoked to get small cell lung cancer.
Non-small cell lung cancer
In the UK, non-small cell lung cancer makes up around 87 out of 100 lung cancer cases.6 There are three different types, although sometimes diagnosing which type you have isn’t possible if not many cells were taken during a biopsy or if the cells are undeveloped. If this is the case, your consultant will tell you that you have undifferentiated non-small cell lung cancer. Because this group of cancers tend to behave in a similar way, it won’t usually influence the type of treatment you need. The three types of non-small cell lung cancer are:
Squamous cell cancer: This cancer is usually caused by smoking and develops in the cells lining your airways. It’s the most common type of primary lung cancer.
Adenocarcinoma: This type of lung cancer is becoming more common in the UK. It develops in the lining of your airways from a type of cell that produces mucus.
Large cell carcinoma: Under a microscope, the cells look large and rounded.
Secondary lung cancer: If your lung cancer has spread from elsewhere in your body, your choice of treatment will depend on where those cancer cells came from. So if you had breast cancer, the cancer cells in your lungs are breast cancer cells will be treated with treatments for breast cancer.
Mesothelioma: This type of cancer is quite rare but becoming more common. It affects the tissue that protects your lungs called the pleura. Many cases are caused by exposure to asbestos at work, which is why it’s thought give times as many men as women get this type of cancer.
Causes and risk factors
Smoking is the biggest cause of lung cancer. It is estimated that around nine out of ten cases are because of smoking.7This includes a small number of people who get lung cancer from breathing in second-hand smoke. Other risk factors include:
- getting older
- exposure to radon gas
- exposure to chemicals like asbestos, silica and diesel exhaust
- air pollution
- having lung disease
- a family history of lung cancer
- previous cancer treatment
- low immunity from illnesses like HIV and AIDS, or from taking immunosuppressant drugs.
5 Cancer Research UK, Types of lung cancer http://www.cancerresearchuk.org/cancer-help/type/
lung-cancer/about/types-of-lung-cancer (simplified fraction from 12 out of 100).
6 Cancer Research UK, Types of lung cancer http://www.cancerresearchuk.org/cancer-help/type/
7 NHS, Lung cancer myths and facts