the immune system can have a hard time discerning bad or mutated cells, ones that look much like us, which are mostly self, but part alien. If it can’t tell the difference or gets tricked in some other way by the cancer so that it ignores the usual signals that halt the division of malignant cells, what follows is uncontrolled and reckless growth that is disruptive to normal tissue architecture and function. The immune system can wind up protecting the malignancy.
