I have a lump on my rib cage. it's a rubbery ball that moves with the skin. i know it could be a cyst or lipoma but what are the chances of cancer?

Low : A movable rubbery mass under the skin is not likely to be cancer, but it would be good idea to have it checked by a doctor and may be have it removed.

Slim chance: What you describe sounds very much like a lipoma, a benign fatty growth. It could possibly be a sebaceous (inclusion ) cyst. The chance of this being malignant would be quite small. Ask your doctor to take a look, but don't lose any sleep over it at this time . Good luck.

See your doc: You are right, a cyst or a lipoma would be the more common than a malignant tumor. You should tell your friendly primary care physician about this new mass.