Answer:
Disclaimer: I haven't had a proper science class in ages and I forgot most of the terms. I probably don't have the correct answer that you're looking for, but this is to the best of my ability.
Mutations in cells can cause cancer as it will compete with other cells for energy and space. It will continually multiply/rapidly grow and can't be rid of as its internal system of apoptosis was hindered during the mutation. Mutations can occur due to damages in the DNA.