I have a similar chunky bit lower on my sternum, just below my implants. It's been investigated over the years but it wasn't until I had a PET scan following my recurrence that I could accept it isn't anything sinister. Being the scar tissue and adhesion queen It makes sense, in my case, that it is just a lump of irritation, but I don't like it either and if I wear a bra for any more than a couple of hours I get bruising over it too.
I've had laser and ultrasound therapy on that spot over the years in an attempt to break it up, but the bloody thing seems there to stay. Hopefully yours is just another weirdo anomaly as well. Mxx
