Lump in my 12 year old breast around areola

My 12 years old period is late and she found a lump under her areola,the surface was quite red and painful as well. Few days has past now the redness is gone and the pain has really gone down almost completely gone except when she really pressed it firmly. She’s always had irregular period but this time she missed it and a lump surfaced,as a mum I am worriedly sick. I have booked a GP appointment to be seen in 10 days time. Has anyone experienced this and what’s the outcome. I read it’s very rare for teens to have BC.