My armpit is also slightly sollen could it be breast cancer I aready have my period I would only like answers from people who know what they r talking about a few people in my family have had breast cancer the bump is small pea sized and it started out as like a bruise and now is just slightly raised that breast is a little bigger the the other one you would not notice the six difference unless you look really closely my arm out is slightly sollen is it breast cancer I'm really worried