My GP said straight away - it's a Sebaceous Cyst, and he sounded so convinced and was so quick that I relaxed. He refered me to have it removed by a plastic surgeon.
When I called my insurance company to get an approval as soon as I said it was my breast the lady on the phone used what I can only describe as her "concerned and sympathetic low voice".
Now obviously my GP knows much more than a lady who approves medical insurance, however I can't get that change of voice out of my head.
Can't get it removed until June, even private!