My 11 year old daughter has been telling me that that the lump under her nipples (the one you get from breast development) has been very sensitive.

Normal: Hormone stimulation can cause the beast buds to be sensitive. Time for a talk about her periods because that will follow.

Normal tissue: Thelarche is the term used for the emergence of breast tissue in the beginning stages of puberty. A spongy bit of true breast tissue is located directly under the nipple on one or both sides. It can be tender to touch & one side may emerge before the other.I see 3-5 /yr come to my office for the same question.Menses is expected to follow in 2.5-3yrs.