Amastia
Amastia refers to a rare clinical anomaly in which both internal breast tissue and the visible nipple are absent on one or both sides.
[3] Amastia is presumably due to failure of embryologic (before birth) mammary ridge development or incomplete involution.
People with amastia often suffer from ectodermal defects, which include various syndromes such as cleft palate, isolated pectoral muscle and abnormal formation of the arms.
However, symptoms such as hypertelorism, saddle nose, cleft palate, urologic disorders and dysfunction of muscle, upper and lower limb have been observed.
[4][6] Cases of unilateral amastia are uncommon, and they are often associated with hypoplasia of pectoral major muscle and/or the thorax.
The symptoms of ectodermal dysplasia can be referred to abnormal development of several ectodermal-derived structure such as hair, teeth, nails and sweat glands.
Other symptoms may include the inability to sweat, vision or hearing loss, missing or underdeveloped fingers or toes and maldevelopment of breast tissue.
Both chest wall and upper limb lost normal function, and this syndrome usually occurs unilaterally.
Mild and partial forms of Poland's syndrome are common, which often been undiagnosed because the clinical feature is only breast asymmetry and a horizontal anterior axillary fold, without severe symptoms.
[9] As the name suggests, Scalp-ear-nipple syndrome is characterized by congenital absence of skin, abnormalities of scalp, malformation of ear structures, and undeveloped nipples.
In the embryological development, mammary glands firstly appear after six weeks of pregnancy in the form of ectodermal ridges.
[5] For example, in normal condition, mammary ridge (milk line) would extend from the bilateral axillary tail to the inguinal region.
Therefore, when amastia patients receive medical ultrasound examination, asymmetry or disproportioned mammary tissue may be found.
Other causes may include intrauterine exposure to teratogenic drugs such as Dehydroepiandrosterone and methimazole / carbimazole treatment during first trimester.
It may be related to gene mutation since often patients with bilateral amastia are diagnosed as autosomal dominant and recessive inheritance.
These injuries may happen when patients receive surgery, such as thoracotomy, chest tube placement, or when they are treated by radiotherapy.
The protein tyrosine receptor type F gene (PTPRF) is particularly important in nipple-areola region development.
[5] Amastia is often associated with Poland's syndrome, which requires appropriate reconstructive procedure to stabilize chest wall, transfer dynamic muscle and reposition nipple areola region.
In order to guide the dissection and make sure the correct location of these tissues, marking of the inframammary crease is required before operation.
