Thanks for your prompt response. Upon further viewing his mass is more the size of a large gum ball (rather than a golf ball) and seems to be perfectly round.
A friend first noticed it about a week ago. I have no idea how long it's been there. It went unnoticed by me because my hand doesn't...
My male cat Monty (age is about 11) has a golf ball sized lump/mass at the base of his tail on the side. It doesn't seem to cause him any pain or discomfort when I touch it. He doesn't hold his tail down and seems perfectly healthy other than vomiting occasionally. Any ideas as to what this...