Could a 12 year old get breast cancer?

Rare if ever: The more common issue at 12 in either males (50%) or females (all) is the appearance of nipple or breast tissue, often on one side weeks or months before the other.Spongy tissue just below the nipple separates this normal event from abnormal masses than appear at other locations. In males this may disappear over 6m to a year while in females further progression of breast development occurs.

Rare: I agree with my colleagues that this is very rare. She could have a fluid filled cyst or a fibroadenoma, which are common, noncancerous lumps in young girls. Have her see her pediatrician.