Adenosis occurs when some of the lobules (milk-producing sacs) grow larger and contain more glands than usual. If the enlarged lobules also contain scar-like fibrous tissue, this is called sclerosing adenosis.
Adenosis may cause a lump that you or your doctor can feel. It also may show up on a mammogram as a distorted area, a mass, or calcifications, the small white calcium deposits that are sometimes associated with an underlying breast cancer. A biopsy is needed to tell the difference between adenosis and cancer. With a true adenosis, any increase in breast cancer risk appears to be slight.