Dear Mrs_Ames77: It is unlikely that this lump is breast cancer. Unfortunately, the only way to know if this is something to be concerned about is to have it evaluated by a physician. Perhaps a partner of her physician could see her sooner - so that the wait and worry could be minimized.
I know it is 6 years later, but my 9 year old daughter now has the same exact kind of lump under her left nipple. She expresses the same exact symtoms. I haven't made a appointment at our doctor yet, but I will tomorrow. Is there anything to be concerned about?