Many congenital and neoplastic breast disorders present in childhood and adolescence. Although the vast majority are benign, any breast anomaly takes on major significance for young girls and their families. Breast development in adolescents is an important marker of transition to adulthood and alterations in normal development can have significant psychological effect. 1 Patients with breast disorders should be promptly diagnosed and counseled on the significance of the anomaly so that potential treatments can ensue in a timely manner. Such efforts permit minimal physical and/or emotional sequelae for the patient. Development of the breast begins around 35 days of gestation, when the ectoderm on the anterior body wall thickens into a ridge known as the ‘milk line,’ ‘milk ridge,’ or ‘Hughes lines.’ 3 This ridge of tissue extends from the area of the developing axilla to the area of the developing inguinal canal. The milk line extends into the axilla and inferior to the inguinal area onto the medial thigh. The ridge above and below the area of the pectoralis muscle recedes while in utero, leaving the mammary primordium, which is the origin of the lactiferous ducts. 4,5 The initial lactiferous ducts form between weeks 10 and 20 and become interspersed through the developing mesenchyme, which becomes the fibrous and fatty portions of the breast. 5 The breast bud, under the stimulation of maternal estrogen, becomes palpable at 34 weeks of gestation. 5 This breast bud regresses within the first months of life, as the estrogen stimulation is no longer present. The nipple appears at 8 months gestation; it is initially a depression and later becomes elevated. Thelarche, or the onset of pubertal breast development, normally occurs between the ages of 8 and 13, with an average age of 10.3 years and is hormonally mediated. 6,7 The initiation of thelarche and progression in females is mediated by race. Research suggests that at all ages, normal thelarche is more advanced in African-American girls than in white girls. In a landmark study by Herman-Giddens et al they reported that approximately 15 % of white girls have thelarche between the ages of 8 and 9 years whereas 48 % of African-American children experience thelarche at this age. The mean age of onset of breast development for African-American girls was 8.9 years, while the average age of thelarche in white females was approximately 10 years. Once thelarche is initiated, adipose tissue and the lactiferous ducts grow in response to estrogen. Progesterone stimulation results in lobular growth and alveolar budding. 7,9 The normal development of the breast, which occurs over a period of 2-4 years, is classified by the Tanner system into five stages (Table 13.1). Maturation can sometimes occur asymmetrically due to fluctuation of the hormonal environments and end organ sensitivity. 10 Lack of development by age 13 is considered delayed and warrants endocrinological evaluation. 11 Menarche usually occurs approximately 2 years after initiation of breast development. Examination of the newborn includes assessment of breast size, nipple position, presence of accessory nipples, and nipple discharge. 1 Examination of the prepubertal female includes inspection and palpation of the chest wall for masses, pain, nipple discharge, and signs of premature thelarche.
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