Has the lump increased in size since you first noticed it? If it has, it means it could be growing and putting pressure on organs so u need to get it checked. My guess is though, you probably did something 15 yrs ago to displace the cartalige between the ribs. In fact i know someone who was doing karate one day and he got punched in the ribs and has a lump there now from the cartilage displacing. I would still get it checked if you havent all ready.
Well I have a lump just below my sternum and it has been there for almost 30 years. It is a lipoma (a fatty cyst). I seem to get them all over. If you lump were cancerous it would not be sitting there so benignly for 15 years.
hi also have lumps on arms and spread all over body have been told its dercums