I am trying to help a MOHS surgeon (I work in gen derm). He is doing MOHS on 2 or 3 separate lesions on the same day, using 17311. Do I use a 59 modifier? I'm having some claims reject even though each of the 17311 codes are linked to different diagnoses. He tells me he's used 51 modifier for years and it's "always been paid". But 51 is denying --- thank you for any help!!