Human breast development.

This review presents an atlas of the histology of the normal physiological states of the human breast including prenatal, prepubertal, and pubertal development, adult resting gland, pregnancy, lactation, and postinvolution. The aim is to produce a pictorial overview of the main stages in development and the common findings in the adult that are considered to be within the range of normality. Unlike inbred strains of animals, in humans it is clear that the chronology of ductal and lobular development is not predictable, either in the fetus, the infant, the peripubertal breast, or the adult. This is probably due to the individual variation in hormone levels both in utero and after birth. For many of the developmental time points there are very little data available. In this review we indicate the current state of knowledge of human breast development and some of the main similarities and differences with the rodent, the main animal model. The major phases of growth and development are described and accompanied by photographs that are representative of each stage. Stress is placed on terminology as there is confusion in the literature. This article is written as an accessory to the companion review on breast cancer.