Congenital Anomalies
Congenital anomalies may be uni- or bilateral and may involve the nipple, the breast or both. Breast abnormalities are classically observed along the line extending from the axilla to the base of the lower limb bud. Congenital defects in the human, however, are overwhelmingly confined to the axillo-pectoral region. Abnormality of volume or form can appear during the development of the mammary gland.

Polythelia. One to 2% of the global population has this abnormality, and an association with renal malformations has been reported in some studies.

Often mistaken for a nevus, the supernumerary nipple is easily distinguished by its color, shape and location in the embryonic ‘milk line’. The aesthetic damage is minor and no surgical correction is generally needed.

Polymastia or Supernumerary Breast. The most frequent localizations are in the axillary or pectoral position. The volume or pain can be sufficient to warrant surgical treatment. A simple axillary prolongation of the mammary gland without nipple is most often reported and discomfort is usual during pregnancy or breastfeeding.

Athelia and Amastia. Isolated athelia is extremely uncommon and absence of the mammary gland is frequently associated. Bilateral amastia is very rare.

An amastia, whether or not associated with athelia, is characteristic of the Poland syndrome. In the complete form, this syndrome associates unilateral mammary aplasia, absence of the sternal and costal portions of the pectoralis major, absence of the pectoralis minor, and absence of portions of the serratus magnus and external oblique muscle: a brachysyndactyly of the hand from the same side is often associated.

The treatment of this syndrome is surgical and the aesthetic result depends on how severely the pectorals and the thorax are affected.

Acquired Abnormalities
Hypotrophy. In hypotrophy, the mammary gland volume is insufficient. The nipple is normal but the definitive breast at stage S5 is small. Mammary hypoplasia is often constitutional and familial. Breast and nipple appearance are normal, as the results of physical examination, but breast volume is quite small. If the physical examination is identical 6 months later in an adolescent more than 17 years, definitive breast size can be concluded.

Breast atrophy is sometimes associated with other pathological situations, such as ovary insufficiency (gonadal dysgenesis or acquired insufficiency) or during hyperandrogenism.

Hypotrophy bordering on amastia can be the consequence of either breast or thoracic surgery in infancy (newborn breast abscess, breast angioma, transmammary thoracic drainage of pleura-pulmonary suppurations, radiotherapy for thoracic tumor) or severe burns. The treatment is principally aesthetic surgery. Oral contraceptives with dominant estrogenic potential may sometimes promote greater mammary development.

Breast Asymmetry. Slight asymmetry is frequent, but when it is very marked, the aesthetic consequences are substantial. The differential diagnosis is unilateral hypertrophy. Palpation of this too voluminous breast reveals normal supple tissue without any nodules. If the morphological aspect of the breast is stage S5, normalization of the two breasts with the same volume is not possible. The only treatment is surgical.

A Becker nevus is frequently associated with unilateral mammary hypoplasia, resulting in asymmetry. This hamartoma appears most often at puberty. Clinically, it is characterized by a clear brown stain, sometimes with layers. Physiopathologically, an increased number of androgenic receptors are present and may be responsible for this underlying condition.

Abnormal Shape. The abnormally shaped breast differs from the harmonious standard breast. The tuberous breast is small with a tight implantation base and a very large nipple. The mammary gland makes a hernia through the nipple. Treatment is surgical.