When I was a clinic assistant in a cancer-focused plastic surgery clinic, it was my job to fight with the insurance companies. I did prior authorizations for every surgery and they would do shit like approve the removal of a melanoma without requiring prior authorization, but performing the skin graft to repair the 10cm diameter hole required a prior authorization because the procedure code falls under the "Plastic Surgery" heading and they wanted to make sure you're not getting skin grafts for cosmetic reasons.