Pic included - any ideas on my lump??

Here is the background information:
1. Started as a tiny bump four years ago. It ripped off when I was brushing my teeth, grew back at about half the current size. 
2. Went to 2 dentists (in 2005) they had no idea.  One suggested cutting it off, the second referred me to an oral surgeon. 
3. Oral surgeon thought it was an "irritation" - treated it for 3 months with no change.
4. Lump was removed with a laser (by oral surgeon) and GREW BACK BIGGER (current size) within six months.  
5. It was biopsied, and is not cancer.  It is not bone - it feels like the rest of my gums. Not painful, not an abscess. I've gone to several dentists, and an orthodontist, a dermatologist, and my family doctor.  Nobody has any ideas. 
6.  It has been the same size for the last three years. 

So there's the mystery.  I absolutely hate it. "Leave it alone and it'll go away" has been my approach, aside from asking every doctor I meet what they think it could be. Anyone have any ideas?