Bit belated in my response, but I have been working with my doctor for a while on the issue. "Benign growths" are unfortunately not an unfamiliar term for me. Had a humongous one in my throat, the ones in my colon, possible one in my thyroid and now the one on my spine. All benign at the moment, but an obvious cancer risk the more I get.

As far as causes go, their best guess is a 1 in 250,000 genetic disorder that deals with tumor suppression. It a best guess because genetic testing didn't actually find a mutation in that particular gene, but because I still have the symptoms, they are declaring a related gene the presumptive cause and giving me the diagnosis anyway.

Still doesn't answer my question completely. It just lends itself to LOTS of diagnostic testing.