Breast development begins between the fifth and seventh weeks of uterine life. At this time, the mammary lines form as bilateral linear condensations of ectoderm extending from the axillary areas to the inguinal regions. This ectoderm comes to lie below the surface of the embryo and at this point they are called the mammary ridges or milk lines which can potentially form the breast tissue (Figure 64.1A). In most instances, however, only a small focus of mammary tissue overlying the thoracic region in the region of the fourth intercostal space (ICS) persists while those in the other areas regress. The tissue aggregate in the fourth ICS continues to divide and thicken, and by the eighth gestational week ectoderm has invaded into the underlying mesenchyme in a branching pattern. At 16 weeks of gestation, 15 to 25 epithelial branches have formed, but canalization has not begun. It is during the third trimester, under the influence of placental sex hormones (mainly estrogen and progesterone), that these epithelial branches are canalized, and primitive breast ducts begin to form. At 32 weeks, differentiation of the parenchyma into lobules begins. The nipple-areolar complex (NAC) begins to form and is completed in the early postnatal period. Branching and canalization continue after birth and through early childhood.1

Breast development is relatively quiescent throughout childhood. Further growth and maturation is initiated at the time of thelarche. With the increased growth at thelarche, the breast progresses through a series of morphological stages, as described by the Tanner classification.2 A Tanner stage 1 breast is prepubertal, with no appreciable breast parenchyma and slight nipple elevation. At thelarche, the breast progresses toward Tanner stage 2 with enlargement of the NAC and elevation of the breast/nipple as a small mound. Tanner stage 3 describes a breast with further enlargement and a smooth transition between the breast and areola without separation of their contours. As the breast continues to enlarge toward Tanner stage 4, the nipple and areola enlarge more and project as a secondary mound above the breast contour. Finally, at the final Tanner stage 5, the breast achieves its mature size and form. The areola has receded and forms a continuous contour with the surrounding breast.2 Most females would have achieved full breast maturity by 16 to 18 years of age; however, the evolution of the breast form continues as a lifelong process.

Various conditions result in hypoplasia or aplasia of the breast. Hypoplasia in the form of mild asymmetry, constricted breast deformities, and mild presentations of Poland syndrome is much more common than aplasia of the breast. Both the constricted breast deformity and Poland syndrome will be discussed in depth below.

Terms used to describe breast aplasia include athelia, isolated absence of the NAC; amasia, absence of breast parenchyma; and amastia, absence of both the breast tissue and the NAC.1 Though this nomenclature would suggest otherwise, athelia and amasia do not seem to occur without each other. These conditions and their distinctions are delineated by Trier.3

Hyperplastic disorders include the excess development of mammary tissue in an otherwise normal anatomic location as well as the development of breast tissue or nipple-areolar structures in locations remote from the normal thoracic distribution. Treatments require simple observation, excision, or breast reduction techniques. Accurate diagnosis and assessment of the severity of the deformity is essential, along with counseling the patient and the family.

Virginal hypertrophy of the breast is a rare condition that results in excessive, rapid, and often non-yielding proliferation of breast tissue. The etiology is unclear, but pathologic
evaluation seems to suggest an abnormal sensitivity of the glandular tissue to the stimulatory effect of estrogen in the setting of normal hormonal levels. The condition may be unilateral or bilateral. Patients often exhibit a rapid onset of breast hypertrophy only months after the initiation of breast growth that quickly becomes symptomatic with the typical signs of macromastia (shoulder and neck pain, bra strap grooving, and rashes) along with tender breast parenchyma, thinned skin, striae, and dilated veins. They will generally present because of the rapid progression.4

Treatment is ultimately surgical. Breast reduction techniques are standard as a first-line therapy, and goals should be to first achieve an improved breast size and symptom relief. Improved symmetry in asymmetric cases of hypertrophy is also important. Some patients require additional breast reduction operations, and mastectomy may be considered in refractory cases.4 Pharmacologic therapy in the form of medroxyprogesterone acetate, dydrogesterone, tamoxifen, and bromocriptine have been employed in the past but side effects have limited their use.1^,4

Like virginal hypertrophy, giant fibroadenomas result from abnormal sensitivity of the breast tissue to normal hormonal levels. This entity is a discrete benign tumor that enlarges rapidly and causes asymmetric enlargement of the breast.5 The treatment is also surgical excision. This is accomplished through breast reduction techniques with a pedicle design and excision pattern that incorporates the mass into the resection specimen and positions the pedicle in the location of the greatest amount of normal breast tissue to preserve breast fullness.5 Concurrent matching procedures on the contralateral breast or delayed mastopexy/augmentative procedures may be required to achieve symmetry. Timing for surgery is driven by the rate of tumor growth. Excision may be necessitated prior to completion breast development to limit the distortion of the breast and to optimize the aesthetic result.

The differential diagnosis for fibroadenoma includes cystosarcoma phyllodes, which can be difficult to differentiate based on a biopsy. Since the incidence of phyllodes tumor is less than 1.3%, treatment should include simple excision of the mass followed by consideration for mastectomy or adjuvant therapy if the diagnosis of a malignant phyllodes tumor is made.6 Consultation with surgical oncology or pediatric surgery is appropriate in this circumstance.

Polythelia, the presence of accessory nipples, is a common pediatric abnormality and has a reported incidence as high as 5.6%.1 Polymastia, the development of supernumerary breast tissue, with or without a nipple or areola, is much less
common. Both are presumed to arise from an incomplete regression of the mammary ridge during embryonic development, leaving residual mammary tissue along the “milk line” between the axilla and inguinal region. Supernumerary nipples typically occur caudal to the true nipple and can present as a partial or complete nipple, partial or complete areola, or a combination. They may be isolated or multiple. While supernumerary nipples are often found during the neonatal period or childhood, accessory breast tissue, either with or without an accessory nipple, is often not identified until the tissue hypertrophies because of puberty, pregnancy, or lactation. Polymastia most often occurs with axillary breast tissue7 (Figure 64.1B). Some authors differentiate the terms “polymastia” and “ectopic breast tissue.” When used strictly, polymastia refers to breast tissue occurring along the “milk line.” “Ectopic breast tissue” refers to the remarkably rare occurrence of breast tissue in other locations in the body.

Supernumerary breast tissue may be removed surgically with placement of closed suction drains. If left in situ, regular monitoring for breast pathology and malignancy must be performed, as this accessory mammary tissue is subject to an equal rate of breast malignancy as the normally positioned gland. Treatment of a mass arising within this tissue must be treated with the same oncologic principles as any breast mass.7

Though usually seen by plastic surgeons in its most severe form, gynecomastia is by far the most common pediatric breast deformity occurring in up to 65% of pubescent males.8 Gynecomastia is a clinical term denoting enlargement of the male breast such that it appears female. It is most often related to proliferation of ductal epithelium as no true acinar development occurs. Most often it is idiopathic in its etiology, but the proliferation can be a symptom of an underlying pathologic process. “Physiologic” gynecomastia is common during three periods of a male’s lifespan. Neonates often exhibit small enlargement of the breast bud and may secrete colostrum transiently as a response to maternal estrogens. As stated above, the fluctuating hormonal milieu of early puberty produces gynecomastia in up to 65% of males between 14 and 16 years of age, and declining androgen production seen in later life can lead to a relative estrogen excess and to the development of gynecomastia. If other signs of pubertal development are present, a standard history and physical suffices for evaluation, but in the absence of normal pubertal development, a more extensive evaluation is required. In most males, pubertal gynecomastia is mild and transient.1

While gynecomastia may be considered normal in these age groups, a history and physical exam should be performed to rule out common causes such as testicular cancer, pituitary tumors, adrenal tumors, liver disease, paraneoplastic syndromes, Klinefelter’s syndrome, thyroid disease, renal failure, myotonic dystrophy, human immunodeficiency virus, marijuana use, alcohol, anabolic steroids, and medications known to cause gynecomastia.1^,8 The most common etiology of gynecomastia in adolescents is idiopathic, while in patients over 40 years of age it is most often drug induced.

When significant gynecomastia persists for 2 years beyond puberty, surgery is often indicated to recreate a normal chest contour and nipple location with limited scaring. The first procedures described for gynecomastia focused on subcutaneous mastectomy through periareolar or various other incisions.1 This remains the best approach in cases of dense fibrous tissue that is located in a subareolar plane. Others have advocated the use of ultrasound-assisted liposuction as the standard first-line approach followed by secondary excision only for a marked residual deformity.8 The ideal approach in most cases is a combination of these, with direct periareolar excision of the central, fibrous breast bud followed by liposuction to contour the peripheral breast area representing the authors’ preferred method. Severely redundant skin may be excised primarily with a periareolar or vertical skin excision, but we believe that the significant elasticity of youthful skin often allows adequate retraction of skin excess such that primary skin excision is not warranted in most cases. If the skin redundancy persists beyond 6 to 12 months postoperatively, excision is undertaken.9 Care is taken during resection to avoid over-resection and the creation of a “dishing” or nipple retraction. Regardless of the technique used, postoperative care involves the use of closed suction drains following excision, prolonged compressive garment application (for at least 6 weeks), and twice-daily deep tissue massage instituted at 1 week postoperatively along with abstinence from heavy exercise for 1 month. These adjuncts aid in tissue re-draping, reduce edema, and limit formation of seroma and hematomas. The cited references8^,9 provide an excellent overview of the subject.