Breast cancer is the most common cancer in women. The diagnosis of breast cancer is always a shock for the patient and her family. Her family and professional life are profoundly disrupted. The diagnosis of cancer always raises a wide range of questions, many of them distressing. This guide provides the most comprehensive, precise, understandable, validated and up-to-date answers. It provides women and their families with essential medical knowledge to help them understand their illness and the different phases of treatment. The guide, based on questions asked by patients, is intended to facilitate dialogue between patients and doctors, without however claiming to replace the individual and personal relationship between doctor and patient. Its aim is to contribute to the health education of the general public, to raise collective awareness and to help transform the reality of this certainly trying but not insurmountable disease.