Dermatology Compliance: Mohs Documentation + Pathology Coordination

Dermatology practices billing Mohs micrographic surgery operate under CMS coding rules in CMS Pub. 100-04 Chapter 12 and the CPT descriptions for 17311-17315, the National Correct Coding Initiative (NCCI) policy and Medically Unlikely Edits (MUE), the AAD Mohs Appropriate Use Criteria jointly developed with ACMS/ASDSA/ASMS, and — where the practice splits dermatopathology technical and professional components — the anti-markup rules at 42 CFR § 414.50. Compliance turns on AUC documentation, stage-by-stage documentation, and pathology coordination.

What CMS and the specialty bodies actually require for Mohs

CMS pays Mohs micrographic surgery under CPT codes 17311 (first stage, head/neck/hands/feet/genitalia, up to 5 tissue blocks), 17312 (each additional stage on the same anatomic area), 17313 (first stage, trunk/arms/legs, up to 5 blocks), 17314 (each additional stage on trunk/arms/legs), and 17315 (each additional block beyond the first 5 per stage). The defining service is the single physician acting as both surgeon and pathologist — performing the excision and personally interpreting the frozen sections for that case.

The CPT description and CMS guidance both require: tumor diagnosis confirmed (typically by prior biopsy), each stage's tissue mapped and oriented, slides prepared and interpreted by the Mohs surgeon, residual tumor mapped onto a Mohs map, and the procedure continued until clear margins are achieved. Documentation must show the stages performed, blocks per stage, margin status at each stage, and the closure method.

The AAD Mohs Appropriate Use Criteria (published 2012 with periodic updates) score 270 clinical scenarios into appropriate, uncertain, and rarely appropriate. The AUC is not strictly mandatory, but it is the recognized standard of care for Mohs case selection. Cases that score uncertain or rarely appropriate need documented clinical justification — patient factors (immunocompromise, recurrence, aggressive histology), tumor factors (size, depth, infiltrative pattern), or anatomic factors (cosmetically sensitive area, tissue conservation).

NCCI policy and MUE define the daily-limit edits. NCCI bundling rules pair 17311 with excision codes (11600-11646) — the practice cannot bill the Mohs as both Mohs and excision for the same lesion. NCCI also pairs Mohs with pathology codes (88305) for the same tissue; the Mohs payment is global and includes the pathology interpretation by the surgeon.

If the practice splits dermatopathology TC and PC — sending biopsy specimens to an outside pathologist — anti-markup rules at 42 CFR § 414.50 cap the practice's payment for the professional component at the lesser of the performing physician's net charge to the practice, the practice's actual charge, or the Medicare-allowed amount. Stark Law and Anti-Kickback Statute analysis is required for any financial relationship between the practice and the pathology group.

ACMS (American College of Mohs Surgery) fellowship-trained Mohs surgeons are not the only providers of Mohs micrographic surgery for billing purposes, but accreditation surveyors and plaintiff experts treat the ACMS fellowship as the recognized credential. Documentation that the Mohs surgeon completed appropriate training is best practice.

The documents you must maintain

The dermatology Mohs compliance binder should hold:

• Mohs surgeon credentialing file including ACMS fellowship status, ABD certification, state license, DEA registration, hospital privileges if applicable
• Mohs Appropriate Use Criteria tool integration in the EHR with case-level AUC scoring documented
• Mohs case log with date, patient identifier, anatomic location, tumor diagnosis, AUC category, stages performed, blocks per stage, margin status at each stage, closure method, complications
• Photography policy if photographs are taken, with patient consent for clinical photography
• Frozen section laboratory standards under CLIA — the Mohs lab is a CLIA-regulated laboratory; CLIA certificate of compliance or accreditation is required
• Quality assurance program for the Mohs lab including slide quality review, stain verification, and turnaround time tracking
• Pathology coordination memo — written designation of how dermatopathology is handled (in-house TC + Mohs surgeon PC at point of care, in-house TC + outside PC, full outside referral)
• Anti-markup rule documentation if the practice bills outside-PC professional components
• Stark Law / Anti-Kickback Statute analysis for any financial relationship with a pathology group
• AAD Position Statements library including the position statements on appropriate Mohs use and reconstruction
• Reconstruction documentation for any complex repair billed separately from the Mohs — closure of the surgical defect is included in the Mohs global, complex flaps or grafts billed separately must meet medical necessity
• MIPS quality measure submission if MIPS-eligible

In Mohs audits we have responded to, the most common documentation finding is missing stage-by-stage margin documentation. The note says "Mohs surgery performed in 3 stages, clear margins achieved" without the per-stage block count, per-stage margin status, or the map showing residual tumor. The MAC requests the chart and finds the documentation does not support 17312 add-on units.

How audits actually work in Mohs cases

MAC TPE audits target high Mohs volume per provider, high stage counts per case (average stages over 2.0), and Mohs performed in anatomic regions that the AUC scores as rarely appropriate. The MAC pulls a probe of typically 20-40 claims, requests the procedure note, the pathology slides (in some cases the actual slides), the AUC documentation, and the closure documentation if a separate closure was billed.

RAC audits routinely target the 17312 and 17314 add-on stages — the per-stage billing is where overbilling most commonly occurs. The RAC reviews whether each billed additional stage is supported by independent processing and interpretation, or whether multiple "stages" were actually re-cuts of the same tissue. RAC extrapolation can multiply a per-case overpayment finding across the practice's Mohs volume.

OIG investigations of Mohs practices have targeted self-referral patterns. A practice that refers all biopsies to a pathology group with shared ownership, financial relationship, or director-level overlap can face Stark Law and Anti-Kickback Statute exposure. The OIG Mohs-specific work plan items in recent years have included unbundling and inappropriate utilization.

State medical board investigations of Mohs surgeons typically follow a patient complaint about cosmesis, an unexpected outcome, or a referral from a Mohs reconstruction follow-up specialist. Boards review the chart against the AAD AUC and the standard-of-care expectations.

What dermatology practices most often miss is the AUC documentation for cases that score uncertain. The case may have been clinically appropriate, but without the AUC reference and the clinical rationale, the chart cannot defend the choice in a post-payment review.

Common gaps unique to Mohs practice

In Mohs audits and reviews we have responded to, the recurring patterns:

• Mohs performed on trunk for a low-risk superficial BCC — AUC scores this as rarely appropriate; without documented rationale, payment is at risk.
• 17312 add-on stages billed for tissue re-cuts within the same stage — additional stages require independent processing of a new tissue specimen.
• Closure billed separately when the Mohs global already includes simple closure — only complex repair codes (13100-13160) and adjacent tissue transfer codes (14000-14302) are separately billable; simple closure is in the Mohs global.
• Pathology coordination disclosure missing — the practice has an arrangement with an outside pathology group but no anti-markup or Stark Law analysis on file.
• CLIA certificate for the Mohs lab expired or not at the correct complexity level — Mohs labs are CLIA-regulated; certificate must match the highest-complexity test performed.
• Mohs map not in the chart — the map is the contemporaneous documentation of tumor mapping; absence of the map weakens the entire case file.
• No AUC documentation for a Mohs case on the back, leg, or other site that the AUC tool scores as rarely appropriate — even if the AUC consideration occurred, it must be visible in the chart.
• Frozen section quality review not documented — slide quality, stain verification, and the Mohs surgeon's interpretation review are part of CLIA-required QA.
• Reconstruction documentation that does not match the defect — the complex repair note describes a defect smaller than the Mohs case suggests, or vice versa.

Maintenance cadence

• Daily: AUC consideration documented in every Mohs case; Mohs map preserved in chart; pathology interpretation documented per stage
• Weekly: case log reconciliation against billing
• Monthly: Mohs case chart audit (5-10 cases) for AUC documentation, stage support, and closure billing accuracy; CLIA proficiency-testing results review
• Quarterly: stage-count distribution review per Mohs surgeon against peer benchmarks; closure-billing rate review
• Annually: AAD AUC tool update review; CLIA certificate renewal tracking; ACMS/ABD continuing education documentation; HIPAA risk analysis; MIPS measure selection; pathology coordination agreement refresh
• On every staff onboard: Mohs technologist competency assessment if applicable; CLIA personnel-qualification documentation; QA program orientation

State preemption: where state law adds materially

California — California Business and Professions Code § 2052 governs scope of practice for non-physician personnel in the Mohs lab. California requires CDPH licensure for clinical laboratories under Health and Safety Code § 1240; the Mohs lab license must be current.

Texas — Texas Department of State Health Services regulates health-care facilities that perform laboratory testing; Texas facility laboratory rules require CLIA compliance (see, e.g., 26 TAC § 509.49 for ASCs). Texas does not impose a blanket separate clinical-laboratory license on an office-based physician Mohs lab beyond CLIA, but Mohs surgeons providing services in Texas-licensed ambulatory surgical centers face the additional facility-licensure requirements under HSC Chapter 243. Confirm any facility-specific licensure obligation with counsel for the specific practice setting.

New York — New York Department of Health licenses clinical laboratories under Public Health Law Article 5; CLIA certification alone is not sufficient for a Mohs lab operating in New York. NYSDOH conducts laboratory inspections separately from CLIA.

Florida — Florida AHCA licenses clinical laboratories under F.S. § 483. Florida additionally regulates office-based surgery under Department of Health rules; Level I and Level II office surgery (which can include Mohs reconstruction) have facility-registration requirements.

How d3rx fits

The d3rx specialty compliance binder maintains the dermatology/Mohs module: ACMS/ABD credentialing tracker, AUC documentation template, Mohs case log, CLIA certificate tracker, anti-markup rule documentation, Stark/AKS analysis for pathology coordination, MIPS quality measure tracker, and accreditation status (where IAC or other accreditation applies). It is a source-grounded administrative documentation aid. It does not certify compliance, provide legal advice, or replace counsel. See compliance binder for the binder structure or audit defense for MAC/RAC response support.

D3rx compliance guides are administrative documentation aids. They do not certify compliance, provide legal advice, replace counsel, or guarantee an audit outcome. The practice remains responsible for reviewing, adopting, and maintaining its compliance program.