Breast cancer affects one in eight women during their lives. No one knows why some women get breast cancer, but there are many risk factors. Risks that you cannot change include
Other risks include obesity, using hormone replacement therapy (also called menopausal hormone therapy), taking birth control pills, drinking alcohol, not having children or having your first child after age 35, and having dense breasts.
Symptoms of breast cancer may include a lump in the breast, a change in size or shape of the breast, and discharge from a nipple. Breast self-exams and mammography can help find breast cancer early, when it is most treatable. One possible treatment is surgery. It could be a lumpectomy or a mastectomy. Other treatments include radiation therapy, chemotherapy, hormone therapy, and targeted therapy. Targeted therapy uses substances that attack cancer cells without harming normal cells.
Men can have breast cancer, too, but it is rare.
NIH: National Cancer Institute