Blog view

Mohs Micrographic Surgery

Vijayarani Sivakumar

Published On - February 15, 2022

Mohs micrographic surgery is recommended for patients with histologically confirmed recurrent basal cell carcinoma of the face and is appropriate for primary basal cell carcinomas of the face that are larger than 1 cm, have aggressive histology, or are located on the H zone of the face

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, and 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). Specifically, the descriptions for these Mohs-specific Current Procedural Terminology (CPT) codes are:

 • CPT Code 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) (e.g., hematoxylin and eosin, toluidine blue), head, neck, hands, feet, genitalia, oany location with surgery directly involving muscle, cartilage, bone, tendon, major nerves, or vessels; first stage, up to 5 tissue blocks.

• CPT Code 17312 - 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) (e.g., 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; each additional stage after the first stage, up to 5 tissue blocks (list separately in addition to code for primary procedure).

 • CPT Code 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) (e.g., hematoxylin and eosin, toluidine blue), of the trunk, arms, or legs; first stage, up to 5 tissue blocks.

 • CPT Code 17314 - 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) (e.g., hematoxylin and eosin, toluidine blue), of the trunk, arms, or legs; each additional stage after the first stage, up to 5 tissue blocks (list separately in addition to code for primary procedure).

• CPT Code 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) (e.g., 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

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

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.
<!--[if !supportLineBreakNewLine]-->
<!--[endif]-->

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

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
<!--[if !supportLineBreakNewLine]-->
<!--[endif]-->

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)
<!--[if !supportLineBreakNewLine]-->
<!--[endif]-->

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)
Squamous cell carcinoma of skin of upper limb, including shoulder
<!--[if !supportLineBreakNewLine]-->
<!--[endif]-->

Tip: Refer to the ICD-10-CM neoplasm table for the most appropriate diagnosis for the patient’s skin cancer.
<!--[if !supportLineBreakNewLine]-->
<!--[endif]-->

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.

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.