Absence of the breast: A rare condition wherein the normal growth of the breast or nipple never takes place and they are congenitally absent.
Absence of the breast, also called amastia, is frequently not an isolated problem. Unilateral amastia (amastia just on one side) is often associated with absence of the pectoral muscles (the muscles of the front of the chest). Bilateral amastia (with absence of both breasts) is associated in 40% of cases with multiple congenital anomalies (birth defects) involving other parts of the body as well.
Amastia can be distinguished from amazia -- wherein breast tissue is absent, but the nipple is present -- a condition that typically is a result of radiation or surgery.