Code Mohs in 6 Easy Steps

Look for location, stages, and tissue blocks in documentation.

By Susan Ward, CPC, CPC-H, CPC-I, CEMC, CPCD, CPRC

When reporting Mohs surgery for treatment of skin cancer, documentation must confirm that a single provider acted as both the surgeon and pathologist. From there, you need only know the location of the treated lesion, plus the number of “stages” and required tissue blocks, to select an appropriate code.

Step 1:
Confirm the Surgeon and Pathologist Are the Same

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

CPT® categorizes Mohs procedures by location:

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, look to code 17311 and add-on code 17312.

For lesions of the trunk, arms, and legs, select code 17313 and add-on code 17314.

Regardless of location, you might also need to report add-on code 17315, as explained in the Mohs Code Definitions sidebar.

Step 3:
How Many Stages?
How Many Blocks?

Things become more complicated at this step. It helps greatly if you understand what the surgeon/pathologist does in the procedure room.

To spare as much healthy tissue as possible (while still eradicating cancerous cells), the physician removes tissue in stages. The first stage is to excise the lesion. The specimen is divided into smaller portions, called blocks.

Per CPT®, “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 carefully mapped, and each block is examined for cancer cells.

Where the surgeon sees a clear margin (no malignant tissue), no further excision is necessary beyond that block. Where the physician finds malignancy, a further stage is required to remove additional material (this is the second stage, which is again divided into blocks). The process continues until no further cancer cells are identified.

Bottom line: Each time the surgeon excises material counts as a stage. Each slide resulting from an individual stage counts as a block.

Step 4:
Separately Consider
Each Lesion Treated

If the surgeon/pathologist uses the Mohs technique on multiple lesions during the same session, code for each lesion separately.

Step 5: Put It All Together

Using steps 1-4, test your skills with these coding scenarios.

Scenario 1: The patient presents with a basal cell carcinoma of the central portion of the forehead. After prepping the patient and site, the physician removes the carcinoma (first stage) and divides it into four tissue blocks for examination. Upon microscopic examination, the physician finds the margins are clear of carcinoma.

The appropriate coding would be:

CPT®: 17311

ICD-9-CM: 173.31
Basal cell carcinoma of skin of other and unspecified parts of face

Scenario 2: 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.

The appropriate coding would be:

CPT®: 17311 (first stage)

+17312 (second stage)

+17315 (six blocks)

ICD-9-CM: 173.32
Squamous cell carcinoma of skin of other and unspecified parts of face

Scenario 3: The patient presents with three skin cancers: basal cell carcinoma of the right neck, squamous cell carcinoma of the right hand, and squamous cell carcinoma of the left ala. After prepping the patient and the sites, the physician first removes the BCC of the neck. He divides it into two tissue blocks. Under microscopic examination, the margins are negative. Next, the physician removes the SCC of the hand, dividing that stage into three tissue blocks. Under microscopic examination, the margins are negative. Lastly, the physician removes the SCC of the left ala, dividing the stage into six blocks. Under microscopic examination, there is a positive margin. The physician then takes a second stage, which is divided into two blocks. Under microscopic examination the margins are negative.

The appropriate coding in this scenario is:

CPT®:

17311 (neck)

17311-59 Distinct procedural service (hand)

17311-59 (nose)

17312 (second stage of nose)

17315 (extra block of first stage of nose)

ICD-9-CM:

173.41 Basal cell carcinoma of scalp and skin of neck

173.62
Squamous cell carcinoma of skin of upper limb, including shoulder

173.32 (nose)

Tip: Refer to the ICD-9-CM neoplasm table for the most appropriate diagnosis for the patient’s skin cancer.

Step 6:
Be on the Lookout for Separate Procedures

The physician may need to conduct additional procedures during the same encounter as a Mohs procedure. Depending on the procedure and the circumstances, you may be able to separately report additional work.

Biopsy and Histopathologic Exam

Because histopathologic examination is included in the Mohs procedure, you may not separately report pathology codes 88302-88309. Likewise, you would not typically report biopsy separately with a Mohs procedure.

The exception to this rule occurs when there is “no prior pathology confirmation of a diagnosis,” according to CPT®. In such a case, the same-day biopsy (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) may be reported separately, in addition to the Mohs surgery. You must append modifier 59 Distinct procedural service to the biopsy and pathology codes to confirm these procedures are not a routine part of the Mohs procedure.

For example, a new or established patient is seen in clinic for a routine skin check. During the examination, the provider identifies a suspicious lesion of the left cheek. After discussion with the patient on treatment options, the patient consents to a biopsy of the lesion. The area is prepped and draped in a sterile fashion, with the use of a 3 mm punch tool. The provider takes a biopsy of the lesion. The specimen is then prepared for frozen section, and is found to be positive for BCC. With the patient’s permission, the physician performs a single stage Mohs in removing the carcinoma.

In this example, the proper reporting would be:

CPT®:

17311 (for the Mohs surgery of the cheek)

11100-59 (for the biopsy)

88331-59 (for the frozen section of the biopsy)

Stains

Mohs surgery includes “routine stains,” such as hematoxylin and eosin (H&E) or toluidine blue. If the physician performs an additional, atypical stain, you may report the appropriate special stain code. CPT® instructs, “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.”

Repair of Surgical Wounds

CPT® instructs, “If a repair is performed, use separate repair, flap, or graft codes.”

For example, in scenario 3, the surgeon/pathologist closes the surgical wound using a cheek rotation flap measuring 5.2 cm2. In this case, correct coding would allow you to separately report 14040 Adjacent tissue transfer or rearrangement, forehead, cheeks, chin, mouth, neck, axillae, genitalia, hands and/or feet; defect 10 sq cm or less. Because treatment is directed at the suspicious lesion, which was proven to be carcinoma, your diagnosis for the entire encounter would be 173.31.

Mohs Code Definitions

17311 Mohs micrographic technique, including removal of all gross tumor, surgical excision of tissue specimens, mapping, color coding of specimens, microscopic examination of specimens by the surgeon, and histopathologic preparation including routine stain(s) (eg, hematoxylin and eosin, toluidine blue), head neck, hands, feet, genitalia or any location with surgery directly involving muscle, cartilage, bone, tendon, major nerves or vessels; first stage, up to 5 tissue blocks

+17312 each additional stage after the first stage, up to 5 tissue blocks (list separately in addition to code for primary procedure)

Report 17312 only with 17311.

17313 Mohs micrographic technique, including removal of all gross tumor, surgical excision of tissue specimens, mapping, color coding of specimens, microscopic examination of specimens by the surgeon, and histopathologic preparation including routine stain(s) (eg, hematoxylin and eosin, toluidine blue), of the trunk, arms or legs; first stage, up to 5 tissue blocks

+17314 each additional stage after the first stage, up to 5 tissue blocks (list separately in addition to code for primary procedure)

Report 17314 only with 17313.

Codes 17311-17314 define “up to five tissue blocks.” If a single stage must be divided into more than five blocks, you may report an add-on code for each additional block beyond the initial five.

+17315 Mohs micrographic technique, including removal of all gross tumor, surgical excision of tissue specimens, mapping, color coding of specimens, microscopic examination of specimens by the surgeon, and histopathologic preparation including routine stain(s) (eg, hematoxylin and eosin, toluidine blue), each additional block after the first 5 tissue blocks, any stage (list separately in addition to code for primary procedure)

You may report 17315 with all codes 17311-17314, when appropriate.

Susan Ward, CPC, CPC-H, CPC-I, CEMC, CPCD, CPRC, is coding and billing manager for Travis C. Holcombe, MD. She has over 20 years of coding and billing experience, is an AAPC workshop presenter and AAPC ICD-10 expert trainer, and served on the 2007-2009 National Advisory Board. Ward was the 2012 president of the Glendale, Ariz., local chapter, and has held offices with the Phoenix, Ariz., local chapter. She is a member of the 2013-2014 AAPC Chapter Association board of directors, region 8-West.

G.J. Verhovshek, MA, CPC, is managing editor at AAPC and a member of the Fort Myers, Fla., local chapter.

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Renee Dustman

Renee Dustman

Renee Dustman is executive editor at AAPC. She has a Bachelor of Science degree in Journalism and a long history of writing just about anything for just about every kind of publication there is or ever has been. She’s also worked in production management for print media, and continues to dabble in graphic design.
Renee Dustman

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Renee Dustman is executive editor at AAPC. She has a Bachelor of Science degree in Journalism and a long history of writing just about anything for just about every kind of publication there is or ever has been. She’s also worked in production management for print media, and continues to dabble in graphic design.

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