Lumps under armpits on the outside of breasts

I have had them for a few years.  I've just assumed that it is the scar tissue that has formed since that was the route the implants were inserted.  They are tender though and get pretty sore after sleeping with my arms above my head.  I had my ba in 2003.  Does anyone else have these?  I've had two mammograms since the implants.  Unfortunately, I didn't mention the lumps. (Guess they are just now really starting to bother me.)  I don't think it was an issue during the first mammogram.  Both came back just fine.