I have a enlarged collarbone where it meets my sternum. (My left side) It is painful, and warm to touch at times. I haven't had any injuries. It's hard and feels like bone. The lump or protrusion is about double in size, maybe bigger. At first my doctor said it may be a tumor, I've had an x-ray which shows no abnormalities. My physician said It could be arthritis, but I am worried it could be something else. I don't have Arthritis anywhere else, and I have had this for about a year now. Is there anything else I could do or a what kind of specialist could I see. I am 52 year old women. Thank you.