Well...I'll tell you how it went. We brought the cat in and she got nervous on the way there and pooped all over herself in the carrier. The vet and techs tried to clean her up in the back room and she went ballistic slicing up everyone and biting one tech on the wrist. The vet didn't want anything to do with her then but I calmed my kitty enough for the doc to feel the lump through the back door of the carrier. The vet said the lump is too small to be biopsied - it's less than marble sized. I have a choice of letting the lump grow (which it doesn't appear to be growing ) and have it biopsied or have an operation and have it removed and then sent to the lab.
Going thru this again, of course is extremely stressful to the cat - not to mention us - and we feel bad when other people get injured because of our pet.
I will have to bring her in again soon and tranquilize her beforehand at home using Benedryl for her ....maybe I'll take some myself.
Please have the lump biopsied.
And since your cat must be tranquilized for the vet visit, you can have a senior work-up performed, which should include bloodwork, and thyoid check and urinalysis.
Let us know how it goes.
The lump could be anything from a lipoma, to a fibrosarcoma to a mast cell tumor. Hopefully it will be something benign, but if it isn't benign, many non-benign dermal masses can have good outcomes with therapy.