Cats can also get tumors from vaccinations. Typically, all the vaccinations are given between the shoulder blades. Some vets, however, inject the cat’s legs. My vet said he uses a different injection site on the legs for each type of vaccine, so that he can keep track of which vaccine causes tumors, in case they occur.
I had my cats microchipped recently, and the chips are implanted between the shoulder blades.
I had my cats all “chipped” last Fall. The vet showed me the chips. The actual chip is in a rice size glass tube with melted ends. It’s a piece of glass and I’ve never heard of glass causing cancer. I can’t think of anything that would be more inert.