Breast congenital anomaly in short

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Congenital Anomalies of the Breast

Embryological Basis

In utero, an ectodermal thickening forms the mammary ridge (milk line/milk streak) - a bilateral band running from the axilla to the inguinal region. At ~9 weeks, all but the pectoral portion regresses to form one pair of breasts. Aberrant regression (too little or too much) causes the various congenital anomalies.

Sabiston Textbook of Surgery, p. 1372

Classification

1. Deficiency Anomalies (Absent / Underdeveloped)

Term	Definition
Amastia	Complete congenital absence of the breast and nipple (bilateral or unilateral)
Amazia	Nipple present but no underlying breast tissue
Athelia	Absence of the nipple only (breast tissue may be present)
Hypoplasia	Underdevelopment of breast tissue

Result from failure of the mammary bud to develop or premature disappearance of the mammary crest.
May be associated with Turner syndrome (gonadal agenesis), Poland syndrome, or occur in isolation.
The Developing Human: Clinically Oriented Embryology, p. 1187
Creasy & Resnik's Maternal-Fetal Medicine, Box 11.2

2. Excess / Accessory Anomalies

Term	Definition
Polymastia (Polymazia)	Supernumerary (extra) breast(s) anywhere along the milk line
Polythelia (Hyperthelia)	Supernumerary nipple(s) - the most common breast anomaly, seen in 1-6% of the population
Hyperadenia	Mammary gland tissue present without a nipple

Key facts:

Both occur due to incomplete regression of the mammary ridge.
Most commonly found along the inframammary chest and axilla; rarely in groin, thigh, or buttock.
Polythelia: incidence similar in males and females; ~10% of cases are familial.
Accessory tissue responds to hormones (enlarges during puberty, pregnancy, lactation) and can develop the same benign and malignant diseases as normal breast tissue.
Polythelia is associated with renal and urinary tract anomalies - screening is recommended.
Polymazia may also associate with vertebral anomalies, cardiac arrhythmias, and renal anomalies.
Bailey & Love's Short Practice of Surgery, p. 947
Dermatology 2-Volume Set 5e, p. 1284
The Developing Human, p. 1187-1188

3. Poland Syndrome

A predominantly sporadic developmental field defect characterized by:

Unilateral hypoplasia or complete absence of the breast / nipple
Absence of the sternal head of pectoralis major (most consistent finding)
May also involve: pectoralis minor, serratus anterior, costal cartilages of ribs 2-5, subcutaneous chest wall tissue
Ipsilateral symbrachydactyly (short, webbed fingers) - hallmark associated hand anomaly
Pathogenesis unclear; prevailing theory involves disruption of subclavian / internal mammary artery blood supply during development

Management: Breast reconstruction with latissimus dorsi muscle flap + silicone implant.

Poland's syndrome - congenital absence of left breast and pectoralis major

Poland's syndrome showing congenital absence of the left breast and pectoralis major muscle. (Bailey & Love's Surgery)

Bailey & Love's Short Practice of Surgery, p. 947
Sabiston Textbook of Surgery, p. 1372
Schwartz's Principles of Surgery, Embryology section

4. Nipple Anomalies

Term	Definition / Notes
Inverted nipples	Nipple fails to evert above the skin surface after birth or puberty; usually autosomal dominant inheritance; can be feature of congenital disorder of glycosylation Ia; may impair breastfeeding
Widely spaced nipples	Seen in Turner syndrome, Noonan syndrome

5. Other / Miscellaneous

Term	Definition
Symastia	Webbing between the two breasts across the midline
Gigantomastia	Excessive bilateral breast enlargement (may have congenital predisposition)

Quick-Reference Summary Table

Anomaly	Embryological Basis	Key Associations
Amastia / Athelia	Failure of mammary bud	Turner syndrome, Poland syndrome
Polythelia	Incomplete milk-line regression	Renal/urinary tract anomalies (screen!)
Polymastia	Incomplete milk-line regression	Cardiac, renal, vertebral anomalies
Poland syndrome	Developmental field defect (vascular?)	Ipsilateral symbrachydactyly
Inverted nipple	Failure of nipple eversion	Autosomal dominant; breastfeeding difficulty
Symastia	Failure of midline separation	Isolated or syndromic

Sources: Bailey & Love's Short Practice of Surgery 28e, Sabiston Textbook of Surgery, The Developing Human: Clinically Oriented Embryology, Creasy & Resnik's Maternal-Fetal Medicine, Dermatology 2-Volume Set 5e (Bolongia).

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