Cancer is defined as a group of diseases characterized by uncontrolled growth and spread of abnormal cells. Uncontrolled growth of cancer cells can result in death. All cancers involve the malfunction of genes that regulate cellular growth, division and death. Approximately 5% of cancers are strongly hereditary in that an inherited gene confers a high risk of developing one or more types of cancer. Cancer arises from gene mutations and stable changes in gene expression that occur during one?s lifetime. These genetic changes may be caused by external agents such as chemicals, irradiation, and viruses; or by internal factors such as hormones or natural metabolic processes. Cancer is treated by surgery, radiation, chemotherapy, hormone therapy, biological therapy, and targeted therapy.