Changes in the fingernails could be symptoms of lung cancer, reveals medical experts. According to experts, including Good Morning Britain’s Dr Amir Khan, any changes that last for three weeks or more would warrant a visit to the doctor. Dr Khan, an NHS doctor turned TV GP, in his latest TV show cautioned the audiance to keep a constant check on bodily functions, even seemingly minor ones such as fingernails. Tobacco smoking accounts for 72 percent of lung cancers diagnosed in the UK in addition to second-hand cigarette smoke, asbestos, silica and diesel exhaust.