The group of diseases involving abnormal growth of cell with the potential to spread to other parts of the body is termed as cancer. Abnormal cell division, and changes at the cellular, genetic and epigenetic levels indicate the process of cancer. Breast cancer is a cancer that develop from breast tissues. There are many symptoms of breast cancer such as change in breast shape, lump in breast, dimpling of skin, newly inverted nipple, fluid discharge from the nipple, or a red scaly patch of skin that indicates the development of breast cancer. Factors such as obesity, a lack of physical exercise, alcoholism, hormone replacement therapy during menopause, ionizing radiation, and a family history of breast cancer are some of its major risk factors. The treatment of breast cancer is surgery followed by chemotherapy or radiation therapy. This book on breast cancer is a resource guide for researchers as well as students. The topics covered herein offer the readers new insights about the advances in cellular and molecular biology of breast cancer.