Cancer begins in cells, the building blocks that make up tissues. Tissues make up the uterus and the other organs of the body.
Normal cells grow and divide to form new cells as the body needs them. When normal cells grow old or get damaged, they die, and new cells take their place.
Sometimes, this process goes wrong. New cells form when the body doesn’t need them, and old or damaged cells don’t die as they should. The buildup of extra cells often forms a mass of tissue called a growth or tumor.
Tumors in the uterus can be benign (not cancer) or malignant (cancer). Benign tumors are not as harmful as malignant tumors:
Cancer cells can spread by breaking away from the uterine tumor. They can travel through lymph vessels to nearby lymph nodes. Also, cancer cells can spread through the blood vessels to the lung, liver, bone, or brain. After spreading, cancer cells may attach to other tissues and grow to form new tumors that may damage those tissues.