A result of recent audits by Medicare Recovery Auditors uncovered instances of incorrect reporting of Mohs micrographic surgery (MMS). In certain situations, the preparation and/or interpretation of slides of tissues removed during the procedure are being reported by someone other than the physician performing the surgery. These audit results present an opportunity to review the MMS procedure and the proper way to report the service.
Mohs micrographic surgery was developed by Dr. Frederick Mohs in the 1930s and is used in the treatment of complex basal and squamous cell skin cancers. The procedure is unique in that small margins are removed and examined in repeated steps with examination of 100% of the margins in order to excise the entire tumor while minimizing the wound size. The excision and evaluation of the tissue is performed until all of the margins are clear.
When reporting MMS, it is important to always keep in mind that the same surgeon performs both the surgical excision and preparation and interpretation of the pathology slides. These services are included and specified in the descriptors of CPT codes 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, through CPT code 17315.
The MMS CPT codes (17311-17315), include skin biopsy and excision services (CPT codes 11100-11101, 11600-11646, and 17260-17286) and pathology services (88300-88309, 88329-99332). Reporting these latter codes in addition to the Mohs micrographic surgery CPT codes is inappropriate. However, if a suspected skin cancer is biopsied for pathologic diagnosis prior to proceeding to Mohs micrographic surgery, the biopsy (CPT codes 11100-11101) and frozen section pathology (CPT code 88331) may be reported separately utilizing modifier 59, Distinct procedural service, to distinguish the diagnostic biopsy from the definitive Mohs surgery.
Although the CPT Manual indicates that modifier 59 should be utilized, it is also acceptable to utilize modifier 58, Staged or related procedure or service by the same physician or other qualified health care professional during the postoperative period, to indicate that the diagnostic skin biopsy and Mohs micrographic surgery were staged, or planned procedures. Repairs, grafts, and flaps are separately reportable with the Mohs micrographic surgery CPT codes. Therefore, simple, intermediate, and complex wound repair codes may be reported with Mohs surgery CPT codes.
If a biopsy is performed prior to the Mohs surgery for diagnostic purposes, can the biopsy be reported?
Yes, should a skin biopsy and a histologic diagnosis be necessary prior to the excision, in this instance, biopsy code 11100, Biopsy of skin, subcutaneous tissue and/or mucous membrane (including simple closure), unless otherwise listed; single lesion, and frozen section surgical pathology code 88331, Pathology consultation during surgery; first tissue block, with frozen sections(s), single specimen, may be reported in addition to the excisional and/or repair codes. Modifier 59, Distinct procedural service, or 58, Staged or related procedure or service by the same physician or other qualified health care professional during the post operative period, would be appended to distinguish the diagnostic biopsy from the definitive Mohs surgery.
In addition, if the lesion was previously biopsied before the patient was referred for Mohs surgery, rebiopsy may not be clinically reasonable and necessary. If the physician is confident that the lesion is a basal cell carcinoma and schedules a Mohs procedure, there is no need to do a biopsy at all. If after the first stage of the Mohs procedure, it turns out that the lesion is not a basal cell carcinoma and the patient requires a more extensive resection, the procedure could be modified at that time.