8-year old has lump between shoulder blades

I've read of other cases on the site of an injection caused sarcoma. I'm worried. I had an old cat who developed cancerous lump between shoulders. Tumour was too big to be removed and she had to be put to sleep. Here in the uk no warning oif injections causing cancer. After she died I read up on it and discovered in America they have stopped doing it between shoulkder blades. When I got my new kitten I told her about this.She agreed to innoculate her in different parts of body. Some were given on the shoulder blades but only 2 years ago. Today when in for her innoculation the vet felt a lump between her shoulder blades. I am woried sick. She has asked me not to worry and come back in a month to see if lump is bigger. I ned to know more. Don't know whether to wait incase its something else or ask to have her operated on. It helps me to share.Thankyou.She's only 8.

From my own experiences with this, I wouldn't feel that comfortable waiting long on this.  If you can afford it, you might consider having x-rays done to get an idea of how big the lump is. 

Definitely keep an eye on it.  Possibly use a measuring tape to identify its current size.

I would suggest getting a needle biopsy of the lump now if you can afford it.  It could be just scar tissue, but it could also be cancer, and if it is the vaccine associated sarcoma, you will get more time with her if you get it removed immediately rather than waiting to see if it grows.