Mohs Micrographic Surgery: Established Uses and Emerging Trends

Pennington and Leffell have reviewed the literature with regard to the relative efficacy of the Mohs technique vs conventional surgery in the treatment of common and uncommon cutaneous neoplasms. The reason for the success of Mohs surgery can be summarized simply: The Mohs surgeon examines the entire microscopic surgical margin for tumor, whereas the pathologist working with a conventional surgeon does not.. In the 1960s, it was widely held that basal cell carcinoma (BCC), particularly when it presented on the face, had a "endency"to recur following excision. In fact, surgeons had a "endency" to leave tumor behind, rather than BCC having an inherent property to persist. When surgeons receive pathology reports stating "xamined margins are free of tumor,"they should bear in mind that standard histopathologic techniques examine less than 1% of the true margin of the submitted specimen. Contiguous Growth vs 'Skip Areas'
Most tumors grow as a contiguous mass of cells until they become com- etent to metastasize and small groups of cells detach from the main body of the tumor. The property of contiguous growth is vital in the success of Mohs surgery. Small surgical margins (1-2 mm) can be taken as long as the microscopic margins are proven free of tumor. In areas where large margins can cause significant cosmetic or functional defects (eg, eyelid, nose, lip), Mohs is superior to any other surgical technique. But some tumors, such as melanoma and perineural SCC, violate the principle of contiguous growth. These tumors have a documented biologic propensity to form histologic "kip areas"and are not ideal candidates for Mohs surgery. Operating with small surgical margins can leave intransit tumor islands behind. Many Mohs surgeons counter that even in these cases, as long as "tandard margins"are used as initial starting points during excision, controlled microscopic examination of the margins with the Mohs technique will improve recurrence rates compared to incomplete margin examination using conventional histologic preparations. This theory has yet to be proven in a random case-controlled study. Issues of Cost and Overuse
The authors fail to mention timely issues concerning Mohs surgery, its cost, and overuse. Mohs surgeons have gone to great lengths to show that- compared to conventional surgical excision, analysis by a pathologist, and reconstruction by a plastic surgeon- tumor excision, histopatholog- histopathologic analysis, and surgical reconstruction all performed by the Mohs surgeon is cost efficient. These studies try to incorporate the anticipated cost of treating recurrent tumors, which should be higher when the Mohs technique is not used. None of these studies has been conducted prospectively. A commonly cited study estimated the cost of conventional surgery using standard excision margins and typical surgical repairs prior to the actual costs generated during Mohs surgery.[1] Factoring in the number of predicted recurrences in the standard excision group, the costs were comparable. Lastly, some mention about overuse of this technique must be made. Over 50 accredited Mohs surgery fellowships are now operational in the United States. Many physicians perform the Mohs procedure without formal fellowship training. Although there are more than 1 million nonmelanoma skin cancers diagnosed each year, the majority of these tumors are small and histologically nonaggressive, and they do not need Mohs surgery. Nor do they need a more costly plastic surgeon (surgical fee plus operating room charge) to remove them. Low-risk tumors, situated on the extremities and trunk are most efficiently treated by dermatologists in their offices. Simple excision and closure, cryotherapy or electrodessication and curettage are all good, relatively inexpensive options. Nonsurgical modalities, including photodynamic therapy, are also effective in selected cases. Newer treatments now available include topical imiquimod(Drug information on imiquimod) (Aldara), a nonspecific immunomodulator that has received US Food and Drug Administration approval for the treatment of superficial BCC. Conclusions
Unfortunately, many tumors in noncritical areas are being treated with Mohs surgery, dramatically increasing costs. The American College of Mohs Micrographic Surgery and Cutaneous Oncology, which accredits Mohs surgical fellowships, should set strict criteria for its members and monitor adherence to these criteria. Mohs surgery is a superb tool that must be used appropriately to maintain its availability until such time as it may be replaced by even better techniques.