Breast cancer. Adenoid cystic carcinoma of the breast, light micrograph (LM) of a section from an affected breast. Adenoid cystic breast cancer is a rare type of invasive malignant ductal breast cancer which accounts for less than 1% of all breast cancers. Adenoid cystic breast cancer begins in the milk duct of the breast before spreading to the tissues around the duct. Microscopically cells of an adenoid cystic tumor look like cancer cells more commonly found in the salivary glands. These cells are different than those of typical ductal cancers. These cancers have a better prognosis than more common types of invasive ductal cancer and usually do not metastasise. Magnification: x 100 when printed at 10 centimetres wide. Human tissue.