Mohs surgery (CPT 17311-17315) is a high-reimbursement, high-audit procedure. Errors in coding stages, blocks, or the subsequent repair are common and costly. The key is understanding that Mohs codes include the excision and pathology, but never the repair.
Coding by Location and Stages
Head, Neck, Hands, Feet (17311):
- Use 17311 for the first stage, which includes up to 5 tissue blocks.
- Add-on Code: +17312 for each additional stage (and each additional 5 blocks) in this location.
Trunk, Arms, Legs (17313):
- Use 17313 for the first stage, up to 5 tissue blocks.
- Add-on Code: +17314 for each additional stage in this location.
Rare Use Code (17315): This code is only for the histopathology preparation when the same surgeon acts as pathologist for tissue not from a Mohs procedure. It's rarely used.
The Crucial Repair Billing Rule
- The Mohs codes (17311-17314) do not include the repair (closure) of the wound.
- You must bill for the repair separately (e.g., Simple 120xx, Intermediate 120xx, Complex 131xx, Flap 140xx, or Graft 151xx).
- Modifier 59: You must append Modifier 59 (Distinct Procedural Service) to the repair code. This tells the payer the repair was separate from the Mohs excision.
- Failure to use Modifier 59 on the repair code will result in an automatic denial, bundling it with the Mohs procedure.
The "Stage" Defined
"A 'stage' is the complete process of excising a specimen, dividing it into blocks, mapping it, and performing the complete histopathology. If the surgeon finds a positive margin and must return to the patient to take more tissue from the same site, that begins Stage 2."
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