Last revised by Wojciech Micał on 20 Aug 2022

Amastia is a rare congenital condition characterized by the absence of breast tissue, nipple and areola. This may occur unilaterally or bilaterally.


During embryological development, breasts first appear as ectoderm ridges during the 6th week of gestation. This ridge grows thicker and leads to mesodermal compression. With further proliferation of the ectodermal cells there is a growth of the same into the mesodermal layer leading to a formation of clusters which further form lobules. In the fifth month of gestation some cords of ectodermal cells sprout from each of these lobules with the central parts undergoing apoptosis leading to formation of ducts. Similarly on the surface, apoptosis occurs leading to formation of pits which protrude through the nipples after connecting with the formed ducts. An inhibition at any one stage of this development leads to hypoplasia or aplasia of the breast

Unilateral amastia 

Defined as amastia involving just one side. It is often seen to be associated with absence of pectoral muscle in setting of Poland syndrome.

Bilateral amastia

In these cases there is amastia on both sides. It is often associated with many other congenital anomalies.

  • teratogen exposure
  • thoracotomy-associated injuries
  • radiotherapy burns

See also

  • amazia: absence of breast glandular tissue with preservation of nipple-areolar complex

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