I've found that insurance companies are beginning to scrutinize these adjacent tissue transfer codes for excessive use, and in my own work I have seen many cases of procedure notes that do not sufficiently document the work of an advancement flap. Per CPT instructions, the "undermining alone of adjacent tissues to achieve closure, without additional incisions, does not constitute adjacent tissue transfer, see complex repair codes 13100-13160." As I understand it, the operative note should document the work of fashioning the flap via new incisions after the completion of the lesion removal. It is not sufficient for the provider to just say that the wound was closed with a flap, or that the provider simply raised or undermined the wound in order to create a flap - that alone only meets the definition of a complex repair. But to be honest, I also don't think the insurance companies' reviewers completely understand this either, so if you and/or your physician feel that the documentation fully supports the flap code and is defensible, you may just need to escalate it to a higher level of appeal - perhaps have your provider draft a letter from a clinician's perspective that clearly spells out why the procedure meets the CPT definition.