The Appropriate Use Criteria: when is Mohs actually recommended?

Not every skin cancer needs Mohs surgery, and the decision is not left to a surgeon's hunch. Since 2012, a published scoring system called the Appropriate Use Criteria, or AUC, has mapped tumor type, size, and location to whether Mohs is the recommended approach. Understanding how the AUC works explains why the same clinic will send one patient home after a quick office treatment and book another for a full Mohs day, and it is also the reason insurers rarely question a Mohs claim that fits the criteria.

The AUC exists to match the technique to the tumor. Before the criteria were published, the choice of who received Mohs varied widely from one practice to the next. To bring consistency, several dermatology and surgery organizations convened an expert panel that reviewed hundreds of clinical scenarios and rated each one. The result, published in the Journal of the American Academy of Dermatology and archived on PubMed, scores 270 specific situations as appropriate, uncertain, or inappropriate for Mohs. It is the reference a surgeon reaches for whenever a case sits near the boundary between Mohs and a simpler treatment.

Location does most of the work. The criteria divide the body into three risk areas. The high-risk area, sometimes labeled Area H, covers the central face, eyelids, nose, lips, ears, genitals, hands, feet, and nail units, the places where spare skin is scarce and a recurrence would be hardest to treat. The medium-risk area covers the cheeks, forehead, scalp, neck, and shins. The low-risk area is the rest of the trunk and limbs. A tumor on high-risk skin almost always scores appropriate for Mohs, which is exactly why Mohs is preferred on the nose, ears, eyelids, and lips. A small, ordinary tumor on the low-risk trunk often does not, which is why a standard excision is a perfectly reasonable choice there.

Tumor type and behavior push the score up or down. Location is not the only input. Aggressive microscopic subtypes such as infiltrative or morpheaform basal cell carcinoma, and poorly differentiated squamous cell carcinoma, score toward appropriate even in lower-risk areas, because these tumors send invisible roots past their visible edge. So do large tumors, poorly defined tumors, and cancers that have already come back after a previous treatment. A tumor carrying several of these features can qualify for Mohs almost anywhere on the body.

Patient factors tip borderline cases. The criteria also weigh the person, not just the lesion. Immunosuppression, whether from an organ transplant or long-term medication, raises the score because these patients develop more cancers and sometimes more aggressive ones. A history of radiation to the site, certain genetic syndromes that cause many skin cancers, and tumors arising in scars or chronic wounds all nudge a case toward Mohs. This is why two people with what looks like the same small tumor can receive different recommendations.

Some cases land in the uncertain zone, and that is by design. Not every scenario is a clean yes or no. The panel deliberately left a middle category for situations where the evidence does not clearly favor one approach, and in those cases the surgeon's judgment, the patient's preferences, and the practical details of the tumor decide. The AUC is a guide, not a rulebook that removes clinical thinking. The American Academy of Dermatology stresses that treatment should always be matched to the individual tumor's risk, which is the same principle the criteria put into a structured form.

The criteria also protect your coverage. Because Mohs is more involved than a simple excision, insurers want to see that it was warranted, and the AUC is the standard they and Medicare rely on. A tumor that clearly meets the criteria is rarely questioned, and when a plan does push back, the surgeon's office can document how your case fits and usually resolve it. To make the criteria easy to apply at the bedside, the American College of Mohs Surgery maintains a free Mohs AUC app that lets a clinician enter the tumor type, subtype, and location and see the appropriateness rating in seconds.

How to use the criteria as a patient. You do not need to memorize the scoring to benefit from it. The useful move is to ask your surgeon a direct question: does my tumor meet the Appropriate Use Criteria for Mohs, and why? A confident answer will reference your biopsy result, the tumor's location, and any aggressive or recurrent features, rather than habit or convenience. If your lesion is small, low risk, and on the trunk, it is fair to ask whether a simpler treatment would serve you just as well. If it sits on the face, looks aggressive under the microscope, or has returned once already, the criteria almost certainly point to Mohs, and choosing an experienced, fellowship-trained Mohs surgeon becomes the next decision.

The reassuring takeaway is that the choice to use Mohs is not arbitrary. It rests on a published, widely accepted framework built to send the most thorough technique to the tumors that truly need it, while sparing lower-risk cancers a longer procedure than they require. When you understand that framework, a Mohs recommendation stops feeling like an upsell and starts looking like what it is: the treatment matched to your particular cancer.

Related reading: Mohs surgery vs standard excision: what is the difference?