Innovations In Mohs Surgery Mary E. Maloney, MD

Innovations In Mohs Surgery

Mary E. Maloney, MD

Mohs surgery was first developed by Dr Frederick Mohs and reported in 1941. 1 His novel approach was to excise a margin of tissue around a tumor and then examine the margin in an en face method designed to evaluate 100% of the margin (rather than the bread loaf technique which samples the margin). He used a chemical fixative that was applied to the skin and left that in place for 24 hours. The tumor and a narrow margin were then excised and processed immediately. In this way, tumor at the margin could be traced in subsequent stages, each stage requiring 24 hours of fixative application. It was a slow process. Drs. Stegman and Tromovich reported the development of the use of frozen sections on fresh tissue, shortening the procedure from days to hours. 2 With either the fixed or frozen technique, examining 100% of the excised margin increased cure rates to 99.9% for primary tumors and 95% for recurrent tumors, with basal cell carcinoma and squamous cell carcinoma being the tumors most commonly treated. 3

So what is new in Mohs surgery is not the technique itself but rather the range of tumors treated with the technique. Melanoma has been treated either with immune stains to highlight tumor cells or with rush permanent fixed tissue examination of the complete margin. While the use of this technique is still gaining acceptance for invasive melanoma, it has dramatically cut the incidence of recurrence in in situ melanoma and is the treatment of choice for such tumors of the head and neck or digits, amelanotic melanoma in situ or recurrent melanoma in situ. 3

There is a growing list of rarer tumors for which Mohs surgery has become the technique of choice. 3 The list includes the rare soft tissue tumors that grow in continuity as well as adnexal tumors. The soft tissue tumors include dermatofibroma sarcoma protuberans (DFSP), cutaneous leiomyosarcoms, atypical fibroxanthoma (AFX), aggressive digital papillary adenocarcinoma and localized dermal sarcoma. This soft tissue tumor may extend well beyond clinical evident margins and has up to a 30% recurrence rate with excision with wide margins. Because these tumors grow in continuity, the method of tissue examination with Mohs surgery allows the surgeon to trace thin strands of tumor through the subcutaneous tissue. This has dramatically reduced the recurrence rate to 3% or less. The cutaneous adnexal tumors similarly have high cure rates with Mohs surgery. This list includes eccrine carcinoma, apocrine carcinoma, porocarcinoma and sebaceous carcinomas. Merkel cell carcinoma and extramammary Paget’s disease both can have skip areas but have been successfully treated with Mohs surgery with close follow-up and adjuvant treatment with radiation therapy. In these cases, Mohs surgery is most useful where wide margins are difficult to obtain, i.e., the ear, nose, lips or other areas where tissue conservation is a must. In 2012, appropriate use criteria were developed with input from all the dermatologic organizations involved with this body of knowledge. 4 These criteria guide the use of Mohs surgery, preventing the overuse of this technique for tumors that can be treated with other modalities. The work has been validated and now is in widespread use. 4 There is even an app to help calculate the score of a tumor and guide the physician to the appropriate treatment.

Pain management and the opioid crisis drove a new study on the recommendations for the use (and more importantly lack of use) of opioid pain relief after Mohs surgery and reconstruction. 5 A panel worked through 87 different procedures (Mohs, excisions and surgical repairs), finding that only 21 of these might require post-operative opioids for pain control. And 20 of the 21 procedures that could require such pain relief would need only the equivalence of ten 5mg oxycodone tablets. This will hopefully reduce the number of prescriptions written and the number of pills dispensed, decreasing the number of unused opioids in medicine cabinets.

Technology is working hard to help identify margins before starting surgery. Confocal microscopy in the reflectance mode uses the differences in reflectance of various tissue types to visualize tumor margins by the captured return signal. This can then guide the initial margin, hopefully decreasing the number of stages required to clear the tumor. While intriguing and offering major advantages, this is still not commercially viable or available due to the expense of the equipment and the time requirements for high-quality images. 6

Knowledge of the biology of cutaneous tumors continues to grow, and this knowledge base reaffirms the benefits of the Mohs surgery technique and its appropriate use for rare tumors and melanomas, as well as basal cell carcinoma and squamous cell carcinoma. At the same time, there has been the establishment of appropriate use criteria to prevent overuse, and an outlining of the rare times opioids are appropriate for pain management. The high cure rates and tissue preservation remain the benefits of the Mohs surgical technique.

Mary E. Maloney, MD, is a professor and chair of Dermatology and a Mohs surgeon at UMass Memorial Health Care.

References:

Mohs RE. Chemosurgery: A microscopically controlled method of cancer excision. Arch Surg 1941:44: 279-295. Tromivitch AT, Stegman SJ. Microscopically controlled excision of cutaneous tumors, Chemosurgery, fresh tissue technique. Cancer 1978; 41: 653-658. Chen ELA, Srivastava D, Nijhawan RI. Mohs micrographic surgery: Development, technique, and applications in cutaneous malignancies. Semin Plast Surg. 2018: 32: 60-68. Connolly Sm, Baker DR, Coldiron BM, et al. AAD/ACMS/ASDSA/ ASMS 2012 Appropriate use criteria for Mohs Micrographic Surgery. J Am Acad Dermatol 2012; 67: 531-550. McLawhorn J, Stephany Mp, Bruhn WE, et al. J Am Acad Dermatol 2010; 82:700-708. Flores E, Yelamos O, Cordova M, et. Al. Peri-operative delineation of nonmelanoma skin cancer margins in vivo with handheld reflectance confocal microscopy and video-mosaicking. J Euro Acad Dermatol Venereo 2019; 33: 1084-1091.