Dermatology Coding Alert

The dermatologist is doing double duty; make sure your coding brings in the deserved reimbursement.

If your dermatologist is skilled enough to perform Mohs micrographic surgery, effectively acting as both the surgeon and the pathologist, she certainly deserves full reimbursement for her services. Read on for our expert answers to frequently asked questions about Mohs surgery.

Question 1: How is Mohs different from other lesion excisions?

Answer 1: Mohs is a treatment procedure for a patient with diagnosed skin cancer. As opposed to a “wide excision,” the goal of Mohs is to remove the entire lesion (ensure clear margins) while preserving healthy tissue, as much as possible. To accomplish this, the physician shaves or excises the lesion, then performs histology to ensure clear margins while the patient is still in surgery. The first excision of a single lesion is the first “stage.”  

Note: Dermatologists will typically not use shaving during Mohs procedures unless it is to obtain the initial diagnosis, says Pamela Biffle, CPC, CPC-P, CPC-I, CPCO, owner of PB Healthcare Consulting and Education Inc. in Austin, Texas. “The only shave I’ve ever seen is for the initial biopsy to get the diagnosis,” she says. “I have never seen a shave as a first stage.”

The physician will take the tissue from the first stage, map and divide the tumor into pieces, and embed each piece of tumor into an individual mounting medium, such as frozen blocks. Each of these pieces of separately embedded tissue from a single stage is a “block,” and the physician typically prepares a few blocks from a single stage.

Whether the physician continues to a second stage depends on the histologic findings. If the margins are clear, the procedure is complete. On the other hand, if the physician finds tumor cells in the margins of any of the tissue blocks, he will go back and remove more tissue from the patient during the same operative session. Each time the physician excises more tissue from the same, you have another “stage” in the Mohs procedure.

Question 2: What are the CPT® codes for Mohs procedures?

Answer 2: The CPT® codes for Mohs procedures are:

• 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, 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)
  
• 17313 — … of the trunk, arms, or legs; first stage, up to 5 tissue blocks
  
• +17314 — … 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)
  
• +17315 — each additional block after the first 5 tissue blocks, any stage (List separately in addition to code for primary procedure)
  

Question 3: What’s the difference between the different Mohs codes? Which code do I use in which situation?

Answer 3: The Mohs codes differ based on:

• The location of the lesion(s)
• The stage of the procedure
• The number of tissue blocks.

So if the dermatologist prepares four blocks during the first stage of a removal of a lesion from the neck, you would report 17311. If he went on to perform a second stage, you would also report +17312. If, during any stage, he prepared more than five blocks, you would report +17315 for each additional block.

Example: In a scenario provided by the AAPC, the patient presents with a basal cell carcinoma of the central portion of the forehead. The dermatologist 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. You would report one unit of 17311, linked to ICD-9 code 173.31 (Basal cell carcinoma of skin of other and unspecified parts of face).

In another AAPC scenario, the patient presents with a squamous cell carcinoma of the nose. The dermatologist removes the carcinoma (first stage) and divides the stage into six tissue blocks. He examines the samples and finds that the margins are not clear. So he removes the positive margin with another excision (second stage), dividing it into three tissue blocks for examination. Those margins prove to be negative (clear).

You would report:

17311 (first stage, first five tissue blocks)
+17312 (second stage, three tissue blocks)
+17315 (the one additional tissue block in stage 1 beyond the five included in 17311).

Link the codes to ICD-9 code 173.32 (Squamous cell carcinoma of skin of other and unspecified parts of face).

Question 4: If Mohs codes are not appropriate, how can you code for multiple same-session excisions? 

Answer: If the dermatologist did not perform the pathology, the Mohs codes would not be appropriate. Unfortunately, under CPT® guidelines, you can only report one procedure to represent the dermatologist’s work. Medicare views same-operative-session excisions and re-excisions as one procedure.

CPT® states, “Use only one code to report the additional excision or re-excision(s) based on the final widest excised diameter required for complete tumor removal at the same operative session.” In this case, the widest margin is 2.4 cm, which should point you to 11643 (Excision, malignant lesion including margins, face, ears, eyelids, nose, lips; excised diameter 2.1 to 3.0 cm).

Alternative: If a re-excision occurs at a subsequent operative session, however, you may report it using modifier 58 (Staged or related procedure or service by the same physician during the postoperative period). 

For example, if the dermatologist in this scenario had to wait three days for the pathology report and a follow-up operative session, you could report the first 1.8-cm excision using 11642 (... excised diameter 1.1 to 2.0 cm), and 11643-58 (... excised diameter 2.1 to 3.0) for the separate-session 2.1-cm excision.

Global tip: You’ll only append modifier 58 to the second procedure if it occurs during the first procedure’s global period. The date of the second procedure resets the global period. You should expect 100 percent reimbursement for procedures you file with modifier 58. Make sure you deserve the reimbursement before you append the 58.

Don’t miss: CMS guidelines state that “if Mohs on a single site cannot be completed on the same day because the patient could not tolerate further surgery and the additional stages were completed the following day, you must start with the primary code (CPT® code 17311) on day two. Computer edits will reject claims where a secondary code (e.g., CPT® code 17312) is billed without the primary code (e.g., CPT® code 17311) also appearing on same date of service, same claim.”