Could my daughter have breast cancer at 14?

Very unlikely: Breast cancer at age 14 would be extremely unlikely. Most often breast firmness with swelling & discomfort is from hormonal changes & puberty, and sometimes fibrocystic nodules. See your family doctor or pediatrician for an examination.

Unlikely: Breast cancer is extremely rare in 14 year old women . The more common cause of a breast mass or lump is a fibroadenoma. If she has a lump to feel she should see a breast surgeon and make the diagnosis and take care of it.