Definition of Amastia

Amastia: A rare condition wherein the normal growth of the breast or nipple does not occur.

Unilateral amastia (just on one side) is often associated with absence of the pectoral muscles. 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.

The condition is thought to be described in the Bible "We have a little sister, and she hath no breasts" (Song of Solomon VIII:8).

Amastia is distinguished from amazia wherein the breast tissue is absent, but the nipple is present. Amazia typically is a result of radiation or surgery.