Breast Development

Development of the breast begins around wk 5 of gestation, when the ectoderm on the anterior body wall thickens into a ridge known as the milk line. This ridge of tissue extends from the area of the developing axilla to the area of the developing inguinal canal. The ridge above and below the area of the pectoralis muscle recedes in utero, leaving the mammary primordium, which is the origin of the lactiferous ducts. The initial lactiferous ducts form between wk 10 and 20 and become interspersed through the developing mesenchyme, which becomes the fibrous and fatty portions of the breast. The breast bud, under the stimulation of maternal estrogen, becomes palpable at wk 34 of gestation. This breast bud regresses within the 1st mo of life, because the estrogen stimulation is no longer present. The areola appears at 5 mo of gestation, and the nipple is seen shortly after birth. It is initially depressed and later becomes elevated.

Thelarche, or the onset of pubertal breast development, is hormonally mediated and normally occurs between the ages of 8 and 13 yr, with an average age of 10.3 years. The initiation of thelarche and progression in females is affected by race, with normal thelarche occurring earlier in African-American girls than in Caucasian or Asian girls.

Once thelarche is initiated, normal development of the breast occurs over 2-4 yr and is classified by the sexual maturity rating (SMR) system into 5 stages. Maturation can sometimes occur asymmetrically owing to fluctuation of the hormonal environments and various end organ sensitivities. Lack of development by age 13 yr is considered delayed and warrants endocrinology evaluation. Menarche usually occurs approximately 2 yr after initiation of breast development.

Breast Examination

A breast examination should be included in the annual examination of all children and adolescents. Examination of the newborn includes assessment of breast size, nipple position, presence of accessory nipples, and nipple discharge. Examination of the prepubertal girl includes inspection and palpation of the chest wall for masses, pain, nipple discharge, and signs of premature thelarche. Examination of the adolescent is performed with the patient in the supine position; the arm ipsilateral to the breast that is being examined should be placed next to the patient’s head. The breast tissue is examined with the flat pads of the middle fingers and the examiner can feel for abnormalities on the breast with a pattern similar to spokes on a wheel, in a circular clockwise pattern with concentric circles or by moving in a rotary fashion around the breast. Whatever the method used, the goal is to palpate all the breast tissue in a uniform fashion. The SMR should be noted and axillary, supraclavicular, and infraclavicular nodes evaluated for lymphadenopathy. The areola should be compressed to assess for nipple discharge.

Self Breast Examination

Controversy exists as to the utility of breast self-examination in the adolescent population. Experts believe that it might be ill advised to encourage breast self-examination in the adolescent due to a potential for unnecessary anxiety and possible unwarranted treatment in a population that is at low risk for malignant disease. The American College of Obstetricians and Gynecologists states that despite a lack of definitive data for or against breast self-examination, breast self-examination may be recommended beginning at age 19 yr. Women with previous exposure to therapeutic chest radiation therapy are advised to begin breast self-examination 10 yr after radiation therapy.

Abnormal Development

Neonatal Breast Abnormalities

The condition in which breasts enlarge in the newborn period is neonatal breast hypertrophy. This is quite common in term infants and can occur as a result of elevated circulating maternal endogenous steroid hormones in late gestation. As maternal estrogen levels fall, prolactin levels can increase and the breasts can produce a clear or cloudy (milklike) nipple discharge (“witch’s milk”). Repeated manipulation of the breast can exacerbate the condition. On occasion, the hypertrophy is associated with mastitis caused by a staphylococcal or streptococcal infection; antibiotics should be administered.

Precocious Puberty

Premature thelarche is usually an isolated condition but it may be the first symptom of precocious puberty. Precocious puberty occurs in 14-18% of girls with premature thelarche (Chapter 556). Serial examinations, with particular emphasis on growth velocity, secondary sex characters such as pubic hair, pigmentation of the labia or areola, or vaginal bleeding are imperative to identify precocious puberty. Unless there are associated signs of precocious puberty, the parents should be reassured and the child should be followed.

Amastia

Complete absence of the breast, or amastia, is rare and is thought to occur from lack of formation or obliteration of the milk line. Amastia is usually unilateral and can be congenital or associated with systemic disorders (e.g., malnutrition, Crohn disease) or endocrine disorders (e.g., congenital adrenal hyperplasia, gonadal dysgenesis, hypogonadotropic hypogonadism). It can be associated with anomalies of the underlying mesoderm, such as abnormal pectoralis muscles seen in Poland syndrome (aplasia of the pectoralis muscles, rib deformities, webbed fingers, and radial nerve aplasia) (Fig. 545-1). Amastia or hypomastia can also be iatrogenic, resulting from injuries sustained during thoracotomy, chest tube placement, radiotherapy, severe burns, and inappropriate biopsy of the breast bud. Treatment is surgical correction.

Figure 545-1 Preoperative frontal view of a patient with left breast hypoplasia secondary to Poland syndrome.

(From Sadove AM, van Aalst JA: Congenital and acquired pediatric breast anomalies: a review of 20 years’ experience, Plast Reconstr Surg 115:1039–1050, 2005.)

Supernumerary breast tissue (polymastia) and accessory nipples (polythelia) occur in approximately 1-2% of the population (Fig. 545-2). The abnormally placed tissue can be seen anywhere along the milk line but is usually noted on the chest, upper abdomen, or just inferior to the normally positioned breast. An association has been made between polythelia and anomalies of the urinary and cardiovascular system. Surgical excision of the accessory breasts or nipple is not usually needed. Resection of accessory tissue may be warranted if the patient has pain or for cosmetic reasons.

Figure 545-2 Accessory nipple located inferior to the left breast.

(From Sadove AM, van Aalst JA: Congenital and acquired pediatric breast anomalies: a review of 20 years’ experience, Plast Reconstr Surg 115:1039–1050, 2005.)