A test known as the Schamroth window test can sometimes identify a rare deformity in the fingers known as digital clubbing.
When you press your fingernails together, you should be able to see a diamond-shaped gap between them. If you don’t see this gap, you could have finger clubbing, which could be a symptom of lung cancer.
Finger clubbing could be a symptom of other conditions, too. So, it’s important to meet with a doctor for further testing.