Dear areyes7, Human breast tissue begins to develop early - in the sixth week of fetal life. So at birth there is already breast tissue present. Technically this tissue could become cancerous, however, the changes leading to breast cancer take many years, so breast cancer in a 2 year old would be very unlikely.
Information regarding normal breast development, normal changes associated with puberty and maturing would be appropriate to discuss with the young person. Part of the information is that there are also normal variations in breast development. Self-breast examination techniques could also be taught, which help to get the young person in the routine of examination, as well as to become familiar with their breasts. It is important to emphasize that there are normal variations and if there is something found on exam that is of concern, to ask questions.