Breast cancer is a type of cancer that forms in tissues of the breast, usually the ducts (tubes that carry milk to the nipple) and lobules (glands that make milk). It occurs in both men and women, although male breast cancer is rare. Breast cancer can be classified into several different types depending on the type of cells it affects (epithelial cells, cells of glandular tissue, muscles cells or cells of connective tissue) or based on proteins on or in the cancer cells. In some cases, a single breast tumour can be a combination of different types or be a mixture of invasive and in situ cancer. And in some rarer types of breast cancer, the cancer cells may not form a tumour at all. Breast cancer is the most common...Read more » type of cancer in women worldwide, with nearly 1.7 million new cases diagnosed in 2012. It occurs more frequently in older women (above the age of 50) and less than 5% of all breast cancers are diagnosed in women younger than 40. In most Western countries, fewer and fewer women have died of breast cancer in recent years (especially in younger age groups) because of improved treatment and earlier detection. How is it treated? The management of breast cancer depends on various factors, including the type and stage of the cancer and the age of the patient. Common treatments include surgery, radiation therapy, chemotherapy, hormone therapy or targeted therapy (e.g. monoclonal antibody therapy).