Types Breast cancers are divided generally into two types: invasive cancers and non-invasive or in situ cancers. Invasive cancers are generally divided into lobular and ductal cancers. Lobular cancers start in the many small sacs in the breast that produce milk. The much more common ductal cancers start in the tubes that carry milk from the lobules to the nipple. Within these broad categories, there are over 30 histologic types as seen under the microscope. About half are infiltrating ductal cancers, meaning that they spread through the duct wall. Another 28 percent are combinations of infiltrating ductal cancers and other types, including mucinous, papillary and lobular.
