The main difference between benign and malignant tumors is that malignant tumors can invade nearby tissues. Their cells can also spread to other parts of the body through the bloodstream or lymphatic system and grow in areas far from where the tumor started, a process known as metastasis.
Benign tumors, on the other hand, may grow quite large but do not metastasize or invade nearby tissues. Their cells generally grow slowly, more like normal tissue, and when a benign tumor is removed, it usually does not grow back and the person is considered cured.
Only malignant tumors are considered cancer, and in some cases they can return after treatment. There are different types of malignant tumors, with different treatment options and chances of cure, and an oncologist can address questions or concerns about the difference between benign and malignant tumors.