I think the last time I was here I mentioned Twitch my Wobbler had a sensitive spot on his back.
I had a real scare and I wanted to tell the Forum about my experience in case this happens to your kitty too. 
Luckily the Pet Rescue lady that I deal with is a vet tech and was able to ease my mind.
I thought he had cancer.

This is what happened-
Both my cats are two year old yellow/orange tabby brothers.
I have had Sammy since he was a kitten and he is much braver and confident than Twitch who lived with another lady for around 2 years and I just adopted him when she returned her 4 kitties to the shelter because the boyfriend had allergies (personally, the boyfriend would have had to go if it was me)
Anyway, Sammy was very jealous at first but came to love Twitch a lot.  He help him clean and they play very hard. 
My vet tech told me that what happened to Twitch is not uncommon and nothing to worry about.
These sores come from Cats playing and scratching each other, when the skin closes the bacteria breed and then the sore opens. 
She said they usually get them on their neck or back.
Twitches sore started out as just a tender place on his back that I discovered while petting and massaging his back.
The next time I noticed it it was a pretty good size lump.
Then a day or two later it began oozing lots of nasty, really bad smelling puss
Then all the hair came off the sore and it was this huge raw opening about 1 1/2 inch in diameter.
The open sore was discovered on Sunday and I was so upset I couldn’t even eat, I cleaned it with Peroxide that night which was very painful for him (she said that was good to use or another first aid cleaner)
What a relief when Monday I called my friend and found out that this is not uncommon and the oozing and hair coming off is a good thing and part of the healing process.
The sore is healing very well now and I am very relieved.
Best Wishes to you all, and hope you never have this happen to your baby, but if you do, now you know not to worry.

I think kitties that roam outdoors or play with other kitties are very susceptable to sores or scratches that become abcessed.  Sometimes, when it gets too infected, the vet needs to lance and drain the sores while the kitty is anesticised.  Had to do it with my boy kitty.  He did very well with the procedure and he had to take antibiotics for about a week.  Healed up perfectly.

Any time you notice something unusual on your cat, he should go to the vet.  With all the emergency hospitals available, and all the vet clinics open 6 if not 7 days/week, most with evening hours, too, anything out of the ordinary should be checked as soon as possible.  Even a slight change in behavior or routine can be a sign of a problem.  I am always amazed at the nuber of people who will sit up all night, or cry for three days, or whatever it is, rather than contact their vet and address the problem directly.  Abscesses are usually self limiting, but they can be quite serious, depending on the location.  At the very least, your vet can make your cat feel better sooner, and give you a better chance that the abscess won’t heal over and have to open and drain a second time.  You should also have him tested for feline leukemia and FIV if yhou haven’t done so recently.  I hope he’s doing well.

I’ll add that I do not recommend hydrogen peroxide for the cleansing of open wounds.  It can damage the outer layer of skin (the epitheliel layer).  Before taking the kitty to the DVM, the area surround an abscess can be cleansed with a mild soap (like Ivory).

Cats who are bitten by FIV-infected kitties are at risk for developing FIV infection, too.  So, you should discuss with your DVM whether testing is appropriate.

Michele Gaspar, DVM, DABVP (Feline)