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Anomalies of the development of the mammary glands

Deviations in the sequential process of intrauterine formation and development of the mammary glands in the fetus lead to the appearance of mammary gland abnormalities observed after birth.

The most common abnormalities of the development of the mammary glands include:

  1. additional mammary glands (polymastia), additional nipples (polithelia);
  2. underdevelopment of the mammary glands (hypoplasia, complete absence of mammary glands (amastia and amazia);
  3. inversion of the nipple.

Additional mammary glands are found in both women and men. In 67% of cases, they are formed along the course of the milk lines (folds of the ectoderm of the outer germ leaf at 5-6 weeks of embryonic development), going from the axillary regions to the inguinal folds, mainly in the armpits.

Depending on the degree of development, the classification of polymastia includes:

Class I-the additional mammary gland is fully formed (represented by glandular tissue, there is a nipple and areola);

Class II-the additional mammary gland is represented by glandular tissue and the nipple (without the areola);

Class III-the extra mammary gland is represented by glandular tissue and the areola (without the nipple);

Class IV-the additional mammary gland is represented only by glandular tissue;

Class V - only the nipple and areola are formed;

Class VI-only the nipple (the epithelium) is formed);

Class VII – only the areola is formed.

Class VIII-represented only by a tuft of hair.

Hypoplasia of the mammary glands or insufficient development of glandular tissue is rare. There may be hypoplasia of one breast or on both sides. Severe cases of hypoplasia are noted in Poland syndrome. The syndrome includes hypoplasia of the breast, the lower third of the pectoralis major muscle, and deformity of the anterior chest wall. Poland's syndrome can be combined with abnormalities in the development of the hand.

Amastia is a rare pathological condition characterized by the absence of glandular tissue in the presence of the nipple and areola. 

Atelia-abnormalities in the development of the nipple-areolar complex.

Amazon - absence of glandular tissue, nipple and areola.

Nipple inversion – insufficient ability of the mesenchymal tissue to support the nipple. This anomaly occurs in 4% of women and men.

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