Uterine Fibroid

I was in the ER recently with severe left abdominal pain.  My Gynecologist has advised that a fibroid that sits on top of my uterus as well as through it has lost its blood supply.  It has become very cystic and seems to have reached an obscure shape.  He has suggested surgery to remove same.  What are the chances of a fibroid becoming cancerous?  He feels that laproscopic surgery is out due to the size, 7 cm.  I am 46 and not interested in having babies.  Are there any other alternatives to removal?   Should I consider a hysterectomy?  I am having my CA 125 checked in the a.m.  He feels that if it is normal we can avoid removing the ovaries and maybe the uterus and cervix.  Your thoughts?