What exactly is atypical hyperplasia of the breast?

Irregular Cells: Atypical hyperplasia (ah) is the term used to describe the development of abnormal cells in the breast. These cells may originate from the breast ducts (atypical ductal hyperplasia) or the lobules (atypical lobular hyperplasia). Ah is not cancer, but it increases the risk of developing breast cancer. Therefore patients with a diagnosis of ah often require more frequent breast cancer screening.

Abnormal cells: Atypical ductal hyperplasia (ADH (vasopressin)) is usually diagnosed when a biopsy of the breast has been done because of an abnormal finding on mammogram or sonogram. ADH (vasopressin) means that some of the breast cells are abnormal, but not cancerous. Women who are found to have ADH (vasopressin) are considered to be at increased risk for the future development of breast cancer and require close follow-up.