My boston terrier had a Nast cell tumor removed around her upper back leg close to her rectum. She said the tumor was necrotic and sloughed off in her hand. What does that mean?

Why didn't you ask the vet, and come away with only partial knowledge of what had been done to your dog, for heavens sake??

It means the cells had died, sloughed off means fell off because they were dried up and nothing more has to be done doodlebug.

When I take my dog to the vet and something has to be done, I make darn sure I know ALL OF IT

It means that the skin that the tumor lived on was dying.

Mast cells are very ugly.. they are very invasive. If the tumor became necrotic, I'd be very, very concerned that this tumor dug deeper into your pet.

Do some research online, learn everything you can about it. It may come back

This isn't too uncommon with mast cell tumours. Did you get it sent off to be analyzed for grading?