The mass has been enlarging slowly for over a year. She has always had a "bump" size of quarter or little smaller, since we got her over 5 years ago.

She is not bothered by the mass. If it should grow further than we would consider the radition treatment.

The vet told my hubby it's to hard to predict life span with this slow growing tumor.

I think all questions were answered

This is description of what she has wrong (Thumper is a she )
B. Chondrosarcoma :
1.Chondrosarcomas are malignant tumors characterized by the formation of cartilage. They
occur more frequently in large, but not giant breed dogs. They have been reported rarely in cats.

2.Site predilection: These tumors more commonly occur on the flat bones with 69% occurring
on the head (nose and mandible), ribs, or pelvis. Metaphyseal regions of long bones may also be affected.