Breast development at Puberty

The correct answer is B

• It is a progressive process initiated during embryonic life.
• Puberty marks the beginning of glandular maturation,full breast differentiation is only attained with pregnancy and lactation.
• At birth the breast is formed by 10-12 ductal elements located beneath the nipple-areola complex
• In boys,breast development does not progress much past the initial 10-12 ductal elements.
• In girls, however, puberty begins at 10-12 yrs of age and development is under the control of the Hypothalmic-pituitary axis
• Estrogen acts locally on mammary gland to increase branching of the ducts and is accompanied by an increase in the stroma
• This is thought to be mediated by an estrogen receptor (ER)
• Again full differentiation of mammary glands and of branching and secretory activity may never be attained without pregnancy
• During pregnancy and lactation the maximum branching capability of the breast is expressed.
• The breast of nulliparous women contains more undifferentiated structures
• The cells in ductal structures of nulliparous women are in a more proliferative phase vs. parous breast that are predominantly in Go-resting phase
• The content of ER in the lobular structures is directly proportional to the rate of cellular proliferation. The more differentiation of the lobule the less ER
• This provides an explanation for the greater susceptibility of these structures to be transformed by chemical carcinogens
• It is the observation that these more immature breast lobules is site of origin of ductal carcinomas.
• It is hypothesized that the differences of differentiation of the ductal structures lead to neoplastic changes

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