Cysts on my baby's tail and back

My NANOOK who is 9 has developed cysts on his. Tail and 1 small on his back that had resolved . He isn’t in pain at all still eats like a horse and begs for treats ! These appear to be filled with. Mostly blood and a bit of tissue and a little pus no pain when I squeeze them and clean him no distress at all except to me being a mess and getting blood everywhere ??? Please help
tonimarie17@hotmail.com
Thanks so much