Is my cat sick?

Hi all,
About ten months ago, I was on this site asking what I should do because I found a large bump behind my cat's ear. And altho my cat never stressed any pain, I took him to the vet and had it removed. For some reason, the nurse at the vet persuaded me to take a histo for the cat's bump. The results were not so good. The doctor told me that hercules had some sort of sinus cancer (i dont' really remember what he said)... but the bump was removed.
But all in all, my cat recovered from the surgery; but i've noticed that hercules is now more bossy and mean towards my other cats. Through the past ten months, i've also noticed that he's lost a lot of weight.
This morning, my mom told me that he found and ate a (i'm assuming live) mouse and tonite, he's crankier than ever. He hisses and growls when i go near him and touch him, easily irritated. I know it's summer and it's hot; but I find that he's not interested in food or snacks today.
Is he sick from the mouse, or from some kind of cancerous pain that i can't see?

thanks
jen

It sounds like the mouse may have caused a problem. You have no idea where that mouse was or what disease it could be carrying. If your cat has stopped eating and isn't acting normal I would really get it to the vet again. Luckily you did last time and your cat's problem was found and treated. You know how important it is to have questionable things checked out by a vet and i think that is just what you need to do.

Best to take him to the vet and get checked out.

Cancer in the sinuses can spread to the brain. While the lump may have been removed, that doesn't mean all of the cancer was removed. Your kitty could very well be having pain. It's also a possibility that the cancer has spread to his little brain and is causing behavioural changes

Best to just get him back to the vet.

Good luck to both of you.