my cat has a lump on her back

Hi! While I was petting my cat 2 1/2 year old cat tonight I noticed she had a lump under the skin on her back between the shoulder blades. The lump is small, round and soft.
She had a hydrocortisone shot about two and a half weeks ago to treat a ear problem. Could this be a side effect from the shot or should I be really concerned about it?
Thanks for your help!

I would consult a vet. Maybe it's just an abscess that needs to be lanced and drained. However, it's best to get a consultation.

Thanks. I'm going to call my vet today and ask him about it.

I just called the vet but he wasn't available so I talked to the vet tech and she said it was probably a reaction to the shot. That maybe some of the hydrocortisone got between the skin and caused a build up but it should go down. My question is how long will it take before it goes down?

Hmmm...you would think if it was trapped between the skin, it would have been reabsorbed by now! I'd just keep an eye on it, and if it seems to be painful or getting larger,I'd take her back to the vet.

I will. This has me concerned because I've heard that a cat could develop a tumor from vaccinations and they can show up as early as two weeks after receiving the shot and my cat had a hydrocortisone shot almost three weeks ago. Can they get these tumors from hydrocortisone or only vaccinations?

this would concern me too.
I'd ask them to look at it. If it is an abcess it can get out of control really quickly.

Bea had an "ordinary" abcess a few months back and they told me to wait a few days to see if it would go down on it's own with the antibiotics...
well it didn't, so I brought her back two days later and there was so much tissue and infected yuck they had to do surgery! they couldn't just drain it anymore and the whole ordeal cost kitty a couple weeks of recovery and me $800...