Once you have received a diagnosis of breast cancer, you want to know what type of breast cancer you have. There are many different types of cancer and each is named for the part of the breast the cancer most resembles. Current thinking suggests that both lobular and ductal tumors start in ductal tissue, but that lobular tumors start in the smaller terminal lobules. Their names reflect what the cancers look like.

Most breast cancer (more than 80 percent) is ductal, appearing with glandular or ductal features under the microscope. Breast cancer that looks more like lobular tissue makes up about 12 percent of breast cancers and has single file invasive features. The remaining breast cancers include mucinous, medullary, papillary types, or are cancers of the tissue surrounding the ductal and lobular tissues.

Lobules and ducts are kinds of glands and the prefix adeno means “related to a gland.” This is why breast cancer is referred to as an adenocarcinoma. Intraductal carcinoma or ductal carcinoma in situ (DCIS) is thought of as a precancer and is more contained within the duct. The cells look abnormal with cancerous features but have not invaded tissue outside the duct. That is, they are in situ, Latin for “in its original place.”

Invasive or infiltrating ductal cancers tend to form a firm mass, often with associated fibrous tissue in the lump. Infiltrating lobular cancer is more insidious, because it sends individual cells out like tentacles into the surrounding tissue without a lot of reaction in that tissue and it can feel more like a thickening rather than a discrete firm mass. With lobular cancer, it is harder for the surgeon to know if it is all excised, because it can't be felt as easily as a hard lump. Lobular cancer has a higher tendency to occur in both breasts.

Other types of breast cancer, including medullary, mucinous, and papillary breast cancers, each have their own microscopic patterns. The answer to which type of breast cancer you have can only be found out by your breast biopsy results.