Hi A cat recently showed up at my house and i took him in, he had a small knot on his hip but it didnt seem to bother him he was running and jumping,but within the last week the knot has gotten huge and his foot has swollen,but is very allert and eating and drinking.I have a vet appt for this evening but it is breaking my heart i am grown very fond of him and i am afiard i am gonna have to have him but to sleep.any ideas on what it might be ?