Coding for Mohs Micrographic Surgery

Mohs surgery is performed to remove complex or ill-defined skin cancer, and the procedure includes both the surgery and histopathologic examination. Both capacities are required in order to bill for these codes, and neither part may be delegated to another individual.

Let’s look at the specific guidelines for coding for Mohs Micrographic Surgery:

According to CPT^®,

“The Mohs surgeon removes the tumor tissue and maps and divides the tumor specimen into pieces, and each piece is embedded into an individual tissue block for histopathologic examination. Thus a tissue block in Mohs surgery is defined as an individual tissue piece embedded in a mounting medium for sectioning.” (CPT 2021, Professional Ed. page. 119)

Repair is not included in the coding. If an intermediate or more complex repair is needed and performed, a repair, flap or graft may be reported separately.

The codes for reporting Mohs procedures have zero global days; if the Mohs physician also performs the medically necessary repair, global days may apply to the repair codes.

If a biopsy has already been done, and the diagnosis is known, do not report a separate biopsy code.

However, if a biopsy is performed on the same day as Mohs surgery because there was no prior confirmation of the diagnosis, bill the skin biopsy that was performed (11102, 11104, 11106) and frozen section pathology code 88331.  Use modifier 59 to distinguish the biopsy from the definitive Mohs procedure. Modifier 59 is used on the biopsy code, because Mohs surgery has higher RVUs, and it is reported without a modifier.

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