Sorry, I think I confused things when I used the word 'mole'. It's totally flat, not raised at all and is totally even with the surrounding skin so it is more like a freckle but a big one. The colour is quite dark. Paddy and the others were itching because of what I believe was mites. A few days after administering Revolution to each of them, the scratching stopped. This mark doesn't seem to bother him at all but I was alarmed when I noticed it.
I think the best route to take will be to have a vet check it to put my mind at ease, as has been suggested here. I'm sure hoping it's just a pigment thing, like a freckle as in the case of Jessika's cat.
I don't think I'll contact the vet who did the surgery on Tiger about it because he is located where we used to live which is many hours away. He's an excellent vet but he does like to upsell and try everything under the sun so even with my discount, it could get expensive.
I'll take him to a local vet in a few weeks time that I've used before on occasion. She's pretty good and I think if she had the higher tech equipment for rhinoscopy, she would have found Tiger's tumor too. She was the first vet I took Tiger too when he was having breathing problems and she suspected a tumor but wasn't sure exactly where it was located and just wasn't equipped to find it.