John Chung, M.D. is a nationally known, Board Certified Dermatologist and Mohs Surgeon. He has been in private practice since 1996. Read more about him on his bio page. Here, he answers a few questions about Mohs surgery, an effective technique for treating many forms of skin cancer.
Is there a difference between Mohs Surgery performed by a trained Dermatologist and cancer removal by a plastic surgeon or an ENT doctor? Are the cure rates for nonmelanoma skin cancers the same for both?
Dr. Chung: There are a number of differences, and the primary one is in cure rates. Nonmelanoma skin cancer removal in the form of an excision performed by a plastic surgeon or an ENT would imply that a specimen of tissue is submitted to a lab where it is processed and the results interpreted by another professional, most likely a pathologist. The results would be available in a few days in this situation. Standard surgical excision yields 91.9% cure rate [5]. Another reference reports the cure rate at 90%. [1]
Mohs surgery is so effective due to the way the specimen is removed and examined under the microscope. This procedure includes surgically removing the skin cancer layer by layer and examining the tissue microscopically until cancer-free tissue is attained. A Mohs surgeon is specially trained as a cancer surgeon, pathologist, and reconstructive surgeon. Therefore, there is no delay in knowing the results. Additionally, the area where the skin cancer was removed is repaired subsequently. When a person leaves the outpatient facility, they have ease of mind their cancer is gone. The cure rate of Mohs surgery is 99% [4].
Another difference between Mohs micrographic surgery and surgical excision is cost. The cost of a surgery performed by a Mohs surgeon compared with traditional surgical excision is equitable. However, because of the increased failure rate of the excision to clear the margins (completely eradicate the cancer), additional costs and time are incurred—which also means an additional surgery or surgeries are necessary for repair [3].
Knowing how tissue is processed in the lab is critical towards an effective outcome. How would you describe the removal technique commonly used in standard excisions, and is there a difference between Mohs surgery and standard excision removal?
Dr. Chung: Determining the margins where a skin cancer stops and where a clear margin is obtained is important in order to achieve a high cure rate. Again, there is a discrepancy between standard excision and Mohs surgery in terms of recurrence rates.
In Mohs surgery, the way the tissue is processed and examined allows the surgeon to evaluate 100% of the margins. Because the surgeon is able to view all the margins of the tissue, he or she is simultaneously able to minimize the amount of healthy tissue that is lost [4]. Mohs surgery uses a method to examine tissue under the microscope called Complete Circumferential Peripheral and Deep Margin Assessment (CCPDMA). This is superior to the standard bread loafing technique which I will explain in a moment.
The removal technique often practiced by labs in the event of tissue evaluation of a standard excision describes a method of determining the margin of a skin cancer known as bread loafing or Post Operative Margin Assessment (POMA). Cutting the tissue in horizontal sections, bread loafing suggests only a few representative slides of the margins are read by the pathologist, thus producing a higher possibility for false negative error rates than the method used in Mohs surgery [6]. A false negative error means that a result is proclaimed to be negative when actually it is positive. In this circumstance, a false negative error would mean that a person would be considered cancer free when, indeed, cancer is still present [8].
A dermatopathologist is a specialist in reading slides under a microscope and diagnosing skin biopsies. Do Mohs surgeons and dermatopathologists mostly agree on their analysis of frozen section slides?
Dr. Chung: In May 2016, Dermatology News published an article citing that among 4,145 slides in five sets of data, only 28 were different between Mohs surgeons and dermatopathologists. This equates to a continuity between the two groups of 99%. They nearly always agree on slide interpretation [7].
What are your thoughts about a Mohs surgeon performing surgery in the hospital versus in an outpatient setting?
Dr. Chung: Just recently, the take-home message published in Dermatology, April 19, 2017, compared the cost of surgery in the outpatient setting as significantly lower ($1,745.00) compared with surgery in the operating room ($11,323.00) [2]. We owe it to our patients to be cost-effective.
References:
1. Bolognia, J. L., Jorizzo, J. L., Schaffer, J. V., Callen, J. P., Cerroni, L, Heymann, W.R., et. Al. (2012). Dermatology (3rd ed., pp. 2447). China: Saunders Elsevier.
2. Kim, I. (2017). Outpatient vs operating room setting for surgical treatment of skin cancer. Dermatologic Surgery. Retrieved May 7, 2017 from www.practiceupdate.com/
3. Nassiripour, L., Amirsadri, M., Tabatabaeian, M., Maracy, M. (2016). Cost-effectiveness of surgical excision versus Mohs micrographic surgery for nonmelanoma skin cancer: A retrospective cohort study. Journal of Research in Medical Sciences, 21:91. doi: 10.4103/1735-1995.192507
4. Overview of Mohs Micrographic Surgery (2017). Mohs Surgery Patient Education by American College of Mohs Surgery. Retrieved May 7, 2017 from skincancermohssurgery.org/
5. Samarasinghe, V., & Madan, V. (2012). Nonmelanoma skin cancer. Journal of Cutaneous and Aesthetic Surgery, 5(1):3-10. doi: 10.4103/0974-2077.94323
6. Smith-Zagone, M., Schwartz, M. (2005). Frozen section of skin specimens. Archives of Pathology & Laboratory Medicine, 129(12): 1536-1543). Retrieved May 7, 2017 from http://www.archivesofpathology.org/
7. Sullivan, M. (2016). Mohs surgeons, dermatopathologists nearly always agree on frozen section analysis. Dermatology News. Retrieved May 7, 2017 from www.mdedge.com/…/mohs-surgeons-dermatopathologists-nearly-always-agree
8. Surgical margin (n.d.). Retrieved May 7, 2017 from https://www.revolvy.com/
