If I carry a mutated gene that can cause cancer, I am certain to get it!

It's a myth!

Most cancers are not hereditary: their development is associated with several risk factors such as aging, smoking, alcohol consumption, poor diet, lack of exercise or exposure to harmful substances.

If you have a gene with a mutation—that is to say, a gene that has undergone a change that prevents it from fulfilling its normal function—associated with certain hereditary cancers (e.g., the BRCA gene for breast cancer), you have a higher risk of developing these types of cancer.

Despite this higher risk, the presence of the mutation is not sufficient to cause cancer, as other risk factors also play a role in its development.