Answer:
The immune system is made up of a network of cells, tissues, and organs that work together to protect the body against infection and maintain overall health. The human body is an optimal environment for pathogens, such as bacteria, viruses, fungi, and parasites to thrive. Your immune system isn't tricked by cancer, it tries to fight off the infection, as the infections gets bigger, your healthy blood cells are not able to fight off the cancer cells.
Explanation: I hope this helps, if not let me know and I will give you a different answer, though this came from my textbook.