Breast cancer is the first cause of cancer-related deaths in women, so it is very important to know the symptoms and causes of women's breast cancer. The cause of breast cancer may be different, but by observing some correct social behaviors, breast cancer can be prevented. More than 10,000 people in Iran are diagnosed with breast cancer every year, and this number increases by 5% every year. Fortunately, the death rate from breast cancer has decreased slightly in recent years. This could be due to more awareness and screening for this type of cancer, as well as the development of better treatment methods. Breast cancer is a disorder in which breast tissue cells change and continue to reproduce. These abnormal cells generally stick together to form a tumor. A cancerous tumor is when these abnormal cells invade other parts of the breast, or when they spread to other parts of the body through the bloodstream or lymphatic system. Breast cancer usually starts in the milk-producing glands (lobules) or the tube-shaped ducts that transport milk from the lobule to the nipple. It is less likely that cancer starts in the fatty and fibrous connective tissue of the breast.