Clubbing is a condition that affects the nails and the tips of the fingers. The nail bed becomes softer and fills in, the nails curve and the tips of the fingers swell.

It can occur in several lung illnesses including lung cancer, mesothelioma (a cancer of the lining of the lung), fibrosis of the lungs and a particular type of inflammation of the airways (bronchiectasis).

There are two main types of lung cancer; small cell lung cancer, and non-small cell lung cancer. Clubbing is seen in people with non-small cell lung cancer but rarely in small cell lung cancer. No one is really sure what causes it and it does not alter what treatment is given or how a person will respond to treatment. An uncommon type of clubbing is linked with a special type of arthritis, called hypertrophic pulmonary osteo arthropathy (HPOA). HPOA usually only occurs in people who have an underlying non-small cell lung cancer.