What is an example of a harmful mutation

An example of a harmful mutation in cells is Cancer. Cancer is caused by the abnormal mutations of cells that occur within the body. When this happens, cell growth within the body is abnormally high and the cells divide at a very fast rate. All humans have cancer cells that can either remain dormant or become malignant. This mutation of cells can spread throughout the body invading different organs and can cause major complications. To this date there are no known cures for cancer. Medications that are available are only there to eradicate some of the cells that have mutated but are not a guarantee that will stop its abnormal mutations or growth.