A view into cancerous breast milk ducts. The lobes of the breast (highlighted first) are made up of smaller lobules (highlighted second). Breast milk is produced in the lobules and carried to the nipple by milk ducts. The camera zooms in further to exhibit a micrograph of the milk ducts (stained purple). Cancerous growths are shown expanding in the milk ducts. Breast cancer most often begins in the milk ducts or the lobules. Cancer in the milk ducts is called ductal carcinoma, and can be non-invasive (in situ) or invasive (infiltrating).