Skip to main content

Mohs Surgery Coding: 8 Coding Tips to Overcome Any Challenges

July 16, 2018

Mohs Surgery Coding Challenges

For a dermatology billing team one of the biggest headaches can involve Mohs surgery coding. While there are only a few codes for these procedures, knowing when and how to use them as well as modifiers or add-ons requires more knowledge and expertise than simply thumbing through the code book.

1. Documenting the provider’s dual role is critical to success

  • The provider performing Mohs procedures must be both surgeon as well as pathologist. Mohs technique requires that the same physician must be both the surgeon (who performs the excision of tissue) and the pathologist (who must immediately examine the excised specimen for determining when there are clear margins).
  • If another physician or other qualified practitioner shares any of these duties, and would otherwise report these services separately, the CPT® is clear: the Mohs codes should not be employed.

2. Know the location of the procedure performed

The second thing coders need to know is the location of the procedures, as the CPT® characterizes Mohs procedures by location.

  • Head, neck, hands feet and genitalia, or other locations with surgery directly involving muscle, cartilage, bone, tendons, major nerves or vessels, use code 17311, add-ons 17312.
  • Lesions of the trunk, arms and legs are coded with17313 and 17314 coded as add-on. Coders may also need to employ add-on code 17315.

(Note that some Medicare payers may differ in required location codes – always check with your Medicare payer.)

3. Know and correctly document the stages as well as the blocks

  • To better understand which codes apply it helps to have a good idea of what the surgeon/pathologist actually does when performing the procedure. The idea is to spare as much healthy tissue as possible, resulting in removal of cancerous tissues in stages; the first stage is the excision of the lesion. Once a specimen is obtained, it is divided into smaller segments, or blocks.
  • As CPT® states: “a tissue block…is defined as an individual tissue piece embedded in a mounting medium for sectioning.” The location of each block within the stage is precisely mapped, with each block closely examined for cancerous cells.
  • Once the margins are clear, without any malignant tissue, no further excision is required beyond that particular block.
  • On the other hand, where a malignancy is found, another stage is necessary for removal of more material, comprising the second stage, also divided into a block. This process is continued until no more cancer cells are found.

Download: Dermatology Practice Turn Around Case Study

Remember: whenever the surgeon excises any material, this counts as one stage. Each slide from a stage is considered a block.

4. Consider each lesion separately when coding, and check for separate procedures

If multiple lesions were treated (using Mohs technique) during the same session, code for each separately.

Note that there may also have been additional procedures performed during the same surgical encounter. These may have to be billed separately, depending on circumstances and type of procedure.

5. Billing for histopathologic exams and biopsies

As a rule, histopathologic exams are included in the Mohs procedure, meaning that coders should not separately report applicable pathology codes (88302-88309).  The one exception is when “no prior pathology confirmation of a diagnosis” existed previously per the CPT®. 

  • A same-day biopsy per CPT® reads:  “(11100 Biopsy of skin, subcutaneous tissue and/or mucous membrane (including simple closure), unless otherwise listed; single lesion, +11101 Biopsy of skin, subcutaneous tissue and/or mucous membrane (including simple closure), unless otherwise listed; each separate/additional lesion (List separately in addition to code for primary procedure)), and frozen section pathology (88331 Pathology consultation during surgery; first tissue block, with frozen section(s), single specimen).”

6. Coding stains

“Routine” stains, such as toluidine blue or hematoxylin and eosin (H&E) are included in Mohs surgery, although if the physician must perform additional (atypical) stains, coding allows the reporting of the appropriate stain code. 

7. Surgical wound repairs 

Per CPT: “If a repair is performed, use separate repair, flap or graft codes.” An example is if the surgeon/pathologist closes a cheek rotation flap sized 5.2cm2, the coder may use separate reporting using code 14040. Note that Mohs repairs are not “bundled.”


One final point: know how a particular Medicare payer uses the different listings for location coverage determinations (LCDs) as diagnosis codes vary among LCDS. Example: Noridian, contractor for AZ, MT, ND, OR, SD, UT, WA and WY lists “aggressive pathology” and “skin lesions” separately. Awareness of this can make the difference between rejection and reimbursement.

The above suggestions are general guidelines; consult your CPT® manuals for complete information as there are many examples of exceptions and special considerations to include in one blog.

8. Getting professional coding and billing assistance

As a leader in the medical billing and practice management industry, M-Scribe has been helping practices of all specialties with their coding, billing, documentation and related practice management needs since 2002.  Our technical teams are able to work with whatever system and software you use, keeping your information secure and in compliance with HIPAA regulations. 

We offer expertise in dermatology billing and coding through our team of certified coders, who understand how to correctly code and file accurate claims, including Mohs, excisions, repairs and related areas. In addition, we’ have had plenty of experience using the newer ICD-10, particularly as it applies to specialty coding – something which is still posing challenges to inexperienced coders.

When you consider how many different elements are involved, including bundling, PQRS, MSSR, EHR and other compliance and payer-specific guidelines that have a direct impact on your revenue, you know the importance of partnering with a trusted RCM service for fast and full reimbursement.

M-Scribe’s experienced consultants are available for a free analysis of your practice’s processes and revenue goals. Contact us today at 770-666-0470 or email me at to learn how you can boost your practice’s reimbursements, leaving you and your busy staff more time for doing what you do best: caring for your patients.


Get the Latest RCM News Delivered

Receive practical tips on medical billing and breaking news on RCM in your inbox.

Get in Touch