What Causes Painful Spots On Side And Along Ribs?

My mother has spots on her side, along ribs, that are painful to touch. There is nothing visible on the skin. These areas have spread and now there are perhaps 12-15 places that hurt when she lays on her side. She had a nuclear x ray and the doctor said that all he knows now is that it isn t cancer. This has been going on for 6 months and is just getting worse.