Aplasia of the breast: A rare condition wherein the normal growth of the breast or nipple never takes place. They are congenitally absent. There is no sign whatsoever of the breast tissue, areola or nipple. There is nothing there.
Breast aplasia (also called, amastia) is frequently not alone as the only 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 is thought to be described in the Bible: "We have a little sister, and she hath no breasts" (Song of Solomon VIII:8).
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.