I found a pea sized knot under the skin on my chest or shoulder, not sure what to call this area. If you place three fingers under your collor bone, out toward your shoulder then it is were your forth finger would fall. I have done a self breast check and can not find anything else there or under my arm. It is very painfull when touched. My bra strap laies over it and that is how I found it because it was causing me pain. There is nothing on the surface of my skin that can be seen. I had to draw a circle around it to keep an eye on the area. If you do press down on it, it causes my shoulder, neck and arm to feel discomfort. I had to give up my health insurance to be able to keep my job, so I did not want to run to the doctor's if it could be caused by something like my bra strap or hurt muscel. Dout it but I'm hoping.