Can Benign Tumors Become Malignant?

Can Benign Tumors Become Malignant? Specific types of benign tumors can turn into malignant tumors. These are monitored closely and may require surgical removal. For example, colon polyps (another name for an abnormal mass of cells) can become malignant and are therefore usually surgically removed. What are the chances of a benign tumor turning malignant?