Guidelines for Coding and Billing Mohs Surgery
Mohs micrographic surgery (MMS) is a highly specialized procedure for treating skin cancer, especially basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). It involves the systematic removal of cancerous tissue layer by layer. Then the surgeon immediately examines the tissue under a microscope to confirm that no cancerous cells remain. Because of its complexity and precision, proper coding and billing for Mohs surgery are essential for accurate reimbursement and compliance with Medicare and insurance guidelines.
This blog provides an overview of the key guidelines for coding and billing Mohs surgery.
CPT Codes for Mohs Surgery
The Current Procedural Terminology (CPT) code set defines specific codes for Mohs surgery based on the number of stages and tissue removed.
Primary CPT Codes for Mohs Surgery:
- 17311: Mohs micrographic surgery, 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: Same locations as 17311; each additional stage after the first stage, up to 5 tissue blocks (add-on code).
- 17313: Mohs micrographic surgery, trunk, arms, or legs; first stage, up to 5 tissue blocks.
- 17314: Trunk, arms, or legs; each additional stage after the first stage, up to 5 tissue blocks (add-on code).
- 17315: Each additional tissue block beyond 5 tissue blocks, any stage (add-on code).
Explanation:
- Use 17311 and 17312 for Mohs surgery on the head, neck, hands, feet, or genitalia. Also use them for any site where the surgery directly involves muscle, cartilage, bone, tendon, major nerves, or vessels. These areas are more complex because of function, cosmetic concerns, and anatomy.
- Use 17313 and 17314 for Mohs surgery on the trunk, arms, or legs. In addition, add 17315 for each tissue block beyond the first 5 in any stage.
For multiple stages (i.e., when the surgeon removes tissue layer by layer), use the initial stage code for the first excision. Then use the additional stage code for each subsequent stage of tissue removal.
Histopathologic Examination and Additional Services
The examination of tissue specimens is an integral part of the Mohs procedure, so the provider should document it properly. Because the Mohs surgeon acts as both surgeon and pathologist, the Mohs codes already include the pathology. Therefore, do not report 88300-88309 for the Mohs frozen sections. However, a separate diagnostic biopsy may be reportable on the same day:
- 88305: Level IV surgical pathology, gross and microscopic examination. Report it with modifier 59 only for a separate diagnostic biopsy when there is no prior pathology diagnosis.
- 88307: Level V surgical pathology, gross and microscopic examination. It is not used for Mohs sections.
- 88304: Level III surgical pathology, gross and microscopic examination. Like 88305, use it with modifier 59 only for a separate diagnostic biopsy when there is no prior pathology diagnosis.
Mohs codes require that one physician performs both the surgery and the pathology review. If a separate pathologist examines the tissue, the procedure does not meet the Mohs definition, so do not report Mohs codes.
Pathology Medical Coding Pathology
Coding for the Reconstruction (Repair) Post-Surgery
After Mohs surgery, the patient may need a reconstructive procedure, particularly on cosmetically sensitive areas like the face. Code these repair procedures separately, based on the complexity of the repair and the anatomical site:
- 12001-12018: Simple repair codes based on the length of the wound.
- 13100-13153: Complex repair codes.
- 14000-14302: Adjacent tissue transfer or rearrangement (flap) codes, used when more extensive reconstructive work is required. Skin grafts are reported with their own codes, such as 15040-15261.
It is important to note that the Mohs codes do not include the repair. Therefore, report the repair codes separately when the provider performs a repair.
Modifiers
Modifiers indicate specific circumstances related to the procedure. For Mohs surgery, these are particularly important to ensure accurate billing and reimbursement. Common modifiers used in Mohs surgery billing include:
- Modifier 59: Used on a same-day diagnostic biopsy and its pathology code (88304 or 88305) when there is no prior pathology diagnosis. It shows that the biopsy is a distinct service from the Mohs procedure.
- Modifier 51: Used for multiple procedures in one session. However, Mohs codes are exempt from modifier 51. Codes 17311 and 17313 are modifier 51 exempt, and the add-on codes 17312, 17314, and 17315 never take modifier 51.
- Modifier 52: Used when a procedure is reduced in its scope or complexity, such as when a Mohs procedure is partially completed.
For example, if the surgeon repairs the Mohs defect during the same encounter, report the repair code as well. Because the Mohs codes are modifier 51 exempt, follow payer rules for any multiple procedure modifier on the repair.
CPT Modifiers CPT Medical Modifiers
Billing for Anesthesia
Surgeons usually perform Mohs surgery under local anesthesia, which is included in the Mohs codes and not billed separately. However, if a separate anesthesia provider is involved, that provider reports the anesthesia service. In addition, the anesthesia provider should document the time and type of service provided. Anesthesia codes include:
- 00100-01999: Anesthesia codes, organized by anatomic site and procedure. The specific code depends on the location of the surgery.
- 99100-99140: Qualifying circumstances add-on codes, such as extreme age or emergency conditions that complicate anesthesia.
Other Considerations in Mohs Surgery Billing
- Documentation: Thorough documentation is essential for billing and coding Mohs surgery. This includes detailed records of the stages of surgery, the size of the excised tissue, pathology reports, and any additional procedures (such as repairs).
- Multiple Lesions: When performing Mohs surgery on multiple lesions, you must report each lesion separately, with the corresponding CPT codes for each stage. The coding should reflect the total number of stages performed.
- Unbundling: Be cautious with unbundling services, which is the practice of coding separately for components of a procedure that are generally included in the base code. Payers often view this as improper coding, and it can result in claim denials or audits.
Insurance Considerations
Each insurance payer may have specific guidelines for the coding and billing of Mohs surgery. It is crucial to verify the payer’s policies regarding:
- Coverage for Mohs Surgery: Ensure that the patient’s insurance covers Mohs surgery, especially for non-face lesions, which may have different reimbursement rates.
- Prior Authorization: Some insurers require prior authorization for Mohs surgery, especially for patients with non-melanoma skin cancer or those receiving multiple stages of surgery.
- Payment Rates: Payment rates can vary based on the site of the surgery (e.g., face vs. other body sites), and some payers may have special payment policies for high-complexity cases.
Common Billing Errors to Avoid
- Incorrect Stage Coding: Failing to report the number of stages correctly can result in underpayment. Report each stage properly, and include the additional stage codes for each layer of excision.
- Under- or Over-Coding Repairs: The provider should document the complexity of the repair, because incorrect coding (e.g., coding a complex repair as a simple one) can lead to issues with payment.
- Reporting Pathology Separately: The Mohs codes include the examination of the excised tissue. Therefore, reporting 88300-88309 for Mohs sections is unbundling and can lead to denials or audits.
Accurate coding and billing for Mohs surgery require a thorough understanding of the procedure, proper documentation, and knowledge of payer-specific guidelines. By adhering to the appropriate CPT codes, modifiers, and billing practices, medical providers can receive fair reimbursement. They can also comply with regulations. Proper coding not only benefits the practice but also ensures that patients receive the necessary care without delay due to administrative errors. Always consult the latest CPT code updates and payer-specific guidelines to remain compliant and maximize reimbursement.
Billing and Coding: Mohs Micrographic Surgery (MMS)