page_title: Amastia
section_title: Mechanism
hierarchical_section_title: Amastia / Mechanism
context_page_description: Amastia refers to a rare clinical anomaly in which both breast tissue and nipple are absent. Amastia can be either isolated or complicated with other syndromes such as ectodermal dysplasia, syndactaly and lipoatrophic diabetes. This abnormity can be classified into various types and each could cause different pathologies. Amastia differs from amazia and athelia. Amazia refers to the absence of one or both mammary glands but the nipples remain present. While athelia refers to the absence of one or both nipples, but the mammary gland remains.
  Amastia is presumably due to failure of embryologic 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 upper limb.
  Treatment for female amastia particularly includes psychological guidance and breast reconstruction. Since having breast represents the ability to nursing, amastia may compromise the mental and physical health for female patients.
context_section_description: Mammary glands are arranged in breasts of the primates to produce milk for feeding offspring. They are enlarged and modified sweat glands. In the embryological development, mammary glands firstly appear after six weeks of pregnancy in the form of ectodermal ridges. The ectodermal ridge grows thicker and compresses to form mesoderm. As the proliferation persists, mesodermal layer continues to form clusters. The clusters grow and become lobules. At the same time, the clusters also form a pit, which protrudes to generate the nipples. Impairment in some of these processes may cause aplasia of the breast tissue, which may result in amastia.
  For example, in normal condition, mammary ridge (milk line) would extend from the bilateral axillary tail to the inguinal region. If this extension does not occur in normal way, the breast would not develop successfully.
  Amastia may also be caused by the inability of producing parathyroid hormone related protein. The absence of this protein will disrupt the normal development of mammary gland. Therefore, when amastia patients receive medical ultrasound examination, asymmetry or disproportioned mammary tissue may be found.
caption: Amastia occurs as a result of failed development of the mammary ridge, which impairs the normal formation of breast tissue and nipple