Defintion of Cancer/Tumor

Cancer is a class of desease characterized by out-of-control cell growth. There are over 100 different types of cancer, and each is classified by the type of cells that is initially affected.

Cancer Harms the body when damaged cells divide uncontrollably to form lumps or masses of tissued called tumors (except in the case of leukimia where cancer prohibits normal blood function by abnormal cells division in the blood stream). Tumors can drow and interfere with the digestive, nerveous, and circulatory systems, and they can release hormones that altern body function. Tumors that stay in one spot and demonstrate limitef growth are generally considered to benign.

cells can experience uncontrolled growth if there are damages or mutations to DNA, and therefore, damage to the genes involved in cell division. Four key types of gene are reponsible for the cell division process: oncogenes tell cells when to devide, tumor suppressor genes tell cells when not to debide, suicide genes control apoptosis and tell the cell to kill itself if something goes wrong, and DNA-repair genes insruct a cell to repair damaged DNA.

Cancer occurs when a cells gene mutations make the cell unable to correct DNA damage and unable to commit suicide. Similarly, cancer is a result of mutations that inhibit oncongene and tumor suppressor gene funtion, leading to unconrollable cell growth.