We just noticed this yesterday and got her (8yo siberian) into the vet today. They haven't tested it yet but are pretty certain it is cancer because it is so rapidly growing and firmly connected to her. They think amputating the tail might be the best option but will assess that at an appointment later this week. She is acting normal other than trying to lick at it. My question is, if this is cancerous and we amputate the tail, do you think she will have a good chance of survival? It breaks my heart thinking about losing her so soon and reading about high grade mast cell tumors has me bawling like a baby. Unfortunately I will be out of town for a few days for work and my wife will have to take care of her and get her to the appointments, so any thoughts from you guys would be greatly appreciated.