When you press your fingernails together, do you see a tiny diamond-shaped window of light?

If you can’t see this ‘diamond gap’, you could have finger clubbing, which can be a sign of lung cancer. Finger clubbing is seen in 35% of people with non-small cell lung cancer (NSCLC), and in 4% of those with small cell lung cancer.

Finger clubbing is when the ends of your fingers swell up, and it happens in stages. First, the base of the nail becomes soft and the skin next to the nail bed becomes shiny. Next, the nails begin to curve more than normal when looked at from the side. Finally, the ends of the fingers may get larger and swell; it’s thought to be caused by fluid collecting in the soft tissues of the fingers.