Septectomy

I need some help from a seasoned Otolaryngologist coder. PLEASE!!

My provider performed a septectomy with removal of a portion of the midline hard palate with the microdebrider drill and then removal of septum all the way up to the skull base where a midline portion of the anterior skull base/anterior cranial fossa was excised. This was performed via transnasal endoscope for septal malignancy.

He is coding 61600 and 30520. I know that 61600 is incorrect, but I just cannot find ANY guidance with how to code a septectomy like this. Please HELP!