Abnormal cell division due to amplification of centrosomes, structures responsible for symmetric cell division in a mouse model of human breast cancer. Amplification of centrosomes results in genomic instability, a hallmark of cancer. Breast cancer is cancer that develops from breast tissue. Signs of breast cancer may include a lump in the breast, a change in breast shape, dimpling of the skin, fluid coming from the nipple, or a red scaly patch of skin. In those with distant spread of the disease, there may be bone pain, swollen lymph nodes, shortness of breath, or yellow skin. Risk factors for developing breast cancer include: female sex, obesity, lack of physical exercise, drinking alcohol, hormone replacement therapy during menopause, ionizing radiation, early age at first menstruation, having children late or not at all, and older age. About 5 to 10% of cases are due to genes inherited from a person's parents.