Breast development during adolescence is an important marker of the transition to adulthood . Abnormalities or anomalies of normal breast development can result in poor self-esteem or make the adolescent feel self-conscious, but most breast lesions in children and adolescents are otherwise benign and self-limited.
An overview of breast disorders in children and adolescents will be presented here. Breast masses in children and adolescents, gynecomastia in male adolescents, and disorders of the breast in adult women are discussed separately. (See "Overview of breast masses in children and adolescents" and "Epidemiology and pathogenesis of gynecomastia" and "Causes and evaluation of gynecomastia" and "Clinical manifestations and diagnosis of a palpable breast mass" and "Overview of benign breast disease" and "Breast pain".)
The breasts start forming in the fifth week of embryonic life. They originate from endodermal elements termed mammary ridges. The mammary ridges extend from the embryonic axilla to the inguinal region, but only the area over the fourth intercostal space develops further, while the rest atrophies. Under the influence of steroid hormones during childhood growth and development, the breast buds enlarge, and glandular elements appear . Adipose tissue and lactiferous ducts (lobes of the mammary gland at the tip of the nipple) grow in response to estrogens, while progesterone stimulation causes lobular growth and alveolar budding .
Thelarche typically begins between the ages of 8 and 13 years, with an average age of onset of 10.3 years . While the breast bud is one of the first signs of puberty, the estimated mean time for full breast development is 4.2 years . Adolescent breast development is described according to the stages developed by Tanner in 1969 (picture 1) . (See "Breast development and morphology" and "Normal puberty".)
A breast examination should be included in the annual examination of all children and adolescents [5,6]. Examination of the newborn includes assessment of breast size, nipple position, presence of accessory nipples, and nipple discharge . Asymmetric breast enlargement and/or a thin milky nipple discharge ("witch's milk") related to stimulation from maternal hormones can occur in both males and females. (See 'Congenital abnormalities' below and "Overview of breast masses in children and adolescents", section on 'Neonates and infants'.)