Where is the mass that you had examined? Does it lie in the middle of your chest or to either side, is it soft, hard or painful? When you say it comes out like a golf club, are we talking a Ping driver? ;-) J/k CT scans can be used to show soft tissue abnormalities, and contrast agents can be administered to acquire additional information. You might recognize a CT scan as a film where structures are depicted as such: air is black, bone is white, soft tissue structures are shades of gray. Jennifer is right to ask about the nature of the mass, because if it is on top of your rib cage, one would evaluate it as associated with breast tissue. maybe more detail would help.
Have you recently had a baby or breastfed? I don't know anything about this but I googled it and the main thing I found was women who had just had babies and they said their protrusion felt like it could be moved. The only ones with updates said they have some type of infection and that the medicine given helped after a couple of weeks. I hope you feel better and I hope the doctors are able to eliminate it for you.