I can't tell much from the pictures, but I'll tell you about Bo's lump. I noticed it on the 4th of July, 2000. It was small, like a pea. I took him to the vet the next day, and she did a biopsy. It showed cancerous cells, so I made an appointment for surgery on July 19th. The time from the appointment to surgery it grew very fast - it was the size of a 50 cent piece by the 19th. After the surgery they sent the mass out for testing and it came back as "very malignant - please advise client" and my heart sank.

The good news is, it's been almost three years and he has been cancer free. we never found out for sure if it was a vaccine sarcoma, but it was at the same spot where the rabies vaccine is given.

On the other hand, Abby has a fat deposit lump on her abdomen. She's had it for years and notheing has ever come of it. I think the vet can tell by how the lump feels (hard, soft, painful for the cat, does it move, or does it seem to be attached to something) what type of lump it is, but to be absolutely sure, a biopsy or the like must be done.