From the Research
Tanner stage 2 is the stage where breasts are one mound, characterized by the formation of a small breast bud with a small area of surrounding breast tissue. This stage is the first visible sign of puberty in girls, typically occurring between ages 8-13, with significant variation among individuals 1. The areola may begin to widen but remains at the same level as the breast tissue without separation between the nipple and the breast. Key factors associated with breast development include being overweight or obese, non-white race, being the firstborn, and younger maternal age at menarche 1. Understanding these normal developmental milestones is crucial for distinguishing typical pubertal progression from precocious or delayed puberty. Some studies have investigated the pubertal development mode of girls with Turner syndrome undergoing hormone replacement therapy, showing that breast development can be normal, although the uterus ultimately develops suboptimally 2, 3. However, these findings do not alter the fundamental characteristics of Tanner stage 2 breast development in the general population. The most recent and highest quality study on pubertal development in girls, published in 2010, provides valuable insights into the factors associated with breast and pubic hair stage and estimates the average duration of puberty 1. In clinical practice, recognizing Tanner stage 2 is essential for monitoring normal pubertal progression and identifying potential deviations from typical development.