The report below describes the 6 easy steps to code Mohs Surgeries accurately, while acknowledging separate procedures, Continue reading below to learn more!

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By: Sheila Haynes, CPC
Coding and Compliance Manager

Mohs Micrographic Surgery (MMS) is a precise, tissue-sparing, microscopically controlled surgical technique used to treat selected skin cancers. It is an approach that aims to achieve the highest possible cure rates, minimize wound size and consequent distortions at critical sites such as the eyes, ears, nose, and lips.

MMS is a two-step process in which:

  1. The tumor is removed in stages, followed by immediate histologic evaluation of the margins of the specimen(s); and
  2. Additional excision and evaluation is performed until all margins are clear. Further, the physician performing MMS serves both as surgeon and pathologist; performing not only the excision but also the histologic evaluation of the specimen(s).

6 Easy Steps to Code Mohs Surgeries Accurately:

Step 1 – Confirm the surgeon and pathologist are the same

Mohs surgery requires that a single physician act as both surgeon (excising tissue) and pathologist (immediately examining excised tissue to determine clear margins).

  • The documentation must clearly state that one physician acted as both the surgeon and the pathologist
  • Per CPT®, “if either of these responsibilities is delegated to another physician or qualified health care professional who reports the services separately, the … [Mohs] codes should not be reported.”

Step 2 – Know the Location

Mohs procedures are categorized by location in CPT®:

  • 17311 and add-on code 17312 are used for lesions of the head, neck, hands, feet, and genitalia, or any location with surgery directly involving muscle, cartilage, bone, tendon, major nerves, or vessels.
  • 17313 and add-on code 17314 are used for lesions of the trunk, arms, and legs.
  • Regardless of location, you might also need to report add-on code 17315 for each additional block after the first 5 tissue bocks, any stage.

Step 3 – Know and Correctly Document the Stages and Blocks

  • To understand which codes apply, It helps to understand what the surgeon/pathologist actually does when performing the procedure
  • To goal is to spare as much healthy tissue as possible, resulting in the removal of cancerous tissue in stages
  • The first stage is the excision of the lesion. Once obtained, the specimen is divided into smaller portions or segments called blocks.
  • CPT® states, “a tissue block…is defined as an individual tissue piece embedded in a mounting medium for section.” The location of each block within the stage is precisely mapped, and each block is closely examined for the presence of cancerous cells.
  • Once the margins are found to be clear, without any malignant tissue, no further excision is required beyond that block.
  • However, if the physician finds malignancy, another stage is required to remove additional tissue, which is the second stage, also divided into blocks.
  • The process is continued until no further cancer cells are identified.
  • Each time the surgeon excises tissue this counts as a individual stage and each slide resulting from an individual stage counts as a block.

Step 4 – Each Lesion is Considered Separately

  • If the surgeon/pathologist uses the Mohs technique on multiple lesions during the same session, each lesion should be coded separately.

Step 5 – Repairs for Mohs Surgery

  • Always code separately for the documented repair when a Mohs surgery is performed
  • Although simple repairs are included (bundled) into almost all integumentary codes, no repair is bundled into Mohs surgery procedures per the NCCI and CPT®
  • Per CPT® guidelines, “If a repair is performed, use separate repair, flap, or graft codes.” (simple, intermediate, complex, flaps and grafts)

Step 6 – Be on the Lookout for Separate Procedures

  • The physician may need to conduct additional procedures during the same surgical session as a Mohs procedure.
  • Depending on the procedure and the circumstances, those services could be coded and billed separately.

Biopsy and Histopathologic Exams: As a rule histopathologic examination is included in the Mohs procedure, you may not separately report pathology codes 88302-88309. Likewise, biopsies are not typically separately reportable with a Mohs procedure.

  • The exception to this rule occurs when there is “no prior pathology confirmation of a diagnosis,” according to CPT®, or if the biopsy was for a separate lesion, the biopsy and pathology may be reported separately.
  • Code for the appropriate type of biopsy documented (11102,11104, 11106)
  • Code for the frozen section pathology (88331)
  • Append modifier -59 Distinct procedural service to the biopsy and pathology codes to confirm these are not a routine part of the Mohs procedure

In such a case, the physician’s documentation should clearly indicate:

  • That the biopsy was performed on a lesion other than the one for which Mohs surgery was performed;
  • If the biopsy is of the same lesion as the Mohs lesion, that a biopsy of that lesion had not been done within the previous 60 days; or
  • If there has been a recent (within 60 days) biopsy of the same lesion as the Mohs lesion, the results of that biopsy were unobtainable despite reasonable effort by the Mohs surgeon.

Coding for Stains: Coding for routine stains, such as toluidine blue or hematoxylin and eosin (H&E) are included in Mohs surgery. However, if the physician needs to perform additional atypical stains, coding guidelines allow for the reporting of the appropriate stain code.

  • CPT® guidelines state, “When a nonroutine histochemical stain on frozen tissue is utilized, report +88314 [Special stains (List separately in addition to code for primary service); histochemical staining with frozen section(s)] with modifier 59.”

Put It All Together

Mohs Surgery Scenario: The patient presents with a squamous cell carcinoma of the nose. After prepping the patient and site, the physician removes the carcinoma (first stage) and divides the stages into six tissue blocks for examination. Upon microscopic examination, the physician finds there are positive margins. He removes the positive margin with another excision (second stage), which is divided into three tissue blocks for examination. Upon microscopic examination, the physician finds the margins are negative. An 2.0cm simple repair is used to close the wound.

The appropriate coding would be:

  • 17311 (first stage)
  • +17312 (second stage)
  • +17315 (six blocks)
  • 12011 (simple repair/nose 2.5cm or less)
  • ICD-10-CM: C44.321 Squamous cell carcinoma of skin nose