Unless the physician describes a branchial cleft cyst and pathology confirms it, you should not bill 42815; you described a pre-auricular (in front of the ear, cheek area) congenital cyst/fistula....you need to look at the integumentary system, 114XX with closure. 1205X, or, depending on if a plasty approach was taken, ie advance flap, rotation flap, look at 14040.
Jennifer
CT ENT