I've had two of these! The first time I was diagnosed with one was in 1993. I remember the doctor telling me that it was about the size of a grapefruit and that it could have hair and teeth and goo. He told me about the absorption of twins, and I remember telling him, "Stop it! You have been reading too many Stephen King novels!" I was freaked out.
Later I was out with my girlfriends, a guy asked me "Hey do you have a twin?" and I smiled at him, and said, "Yes, but I ate her." The expression on his face was priceless.
Unfortunately it was cancerous; however, it was only in the tumor, and they got it all out. Thank the Lord.
In 2003, I had another one. This one was the size of a watermelon (in keeping with the fruit theme, I guess.) and grew that large in one week. I looked like I was 6 months pregnant. I named it Bertha. Bertha was benign. Apparently it was really nasty because I came to while still in the operating room, as they were wiping me down, and I could hear the surgical nurse discussing with another that it was really gross, and it had ruptured.
Just call me the original tumor lady. My friends do. ;^) Hopefully, I'm done with these things. Yuck.
My nephew has had two desmoid tumors removed from his hip. I think this is different but it is very worrisome as it seems to be regrowing again.