I'm new to both pathology and ASC billing. I have billed our -TC portion of the pathology that was done in our ASC. I billed 88305-TC with a POS of 24. I am being denied with Cigna for inconsistent modifier use and an Aetna denial because "treatment has been rendered by the payer to be invalid or inappropriate place of service". What am I doing wrong? Should I be using POS 11? I can't find an answer. Please help.