How Mohs Surgery Transformed From Surgical Quackery Into a First-Line Treatment of Skin Cancer

Mohs surgery is currently considered ideal treatment for many types of skin cancers, the most common form of cancer affecting North Americans today.[1] Cancer patients who undergo Mohs surgery can expect excellent survival rates, extremely small recurrence rates and pleasant cosmetic results. However, time and place matter with regards to how and why medicine is practiced and the transition from established medical dogma to novel discovery is not always smooth. This was certainly the case for Mohs surgery, which contradicted many standards of practice when the technique was first performed during the mid-20th century. Developed by American surgeon Dr. Frederic Edward Mohs (1910-2002), the desire to have a significant impact on skin cancer treatment may have been shaped during Mohs’ formative years as he recalls even as a young boy he knew skin cancers were not always being cured.[2]


Mohs Surgery: The Beauty Behind the Method

Mohs technique was much like traditional cancer excision, but with additional modifications. Mohs first treated a skin tumour with a zinc chloride paste he developed, which killed cancer tissue while making the sample firm and easier to handle. However, Mohs believed the most important effect was its preservation of microscopic features (much like formalin fixes tissue in vitro) allowing tissue to be accurately viewed microscopically.[3] Mohs sectioned tissue horizontally, which allowed 100% of the surgical margins to be viewed under the microscope. Contrast this with traditional pathologic processing of tissue where representative vertical sections are taken every 2-4 mm. This is fine for well-defined tumours, but recurrent tumours have bizarre conformations with thin outgrows extending beyond the tumour bulk that would be missed unless all the margins are analyzed. Additionally, Mohs maintained the orientation of the excised tissue so he could return to a very specific area of the wound to remove additional tissue areas that were cancer-laden.[4] Therefore, the least amount of tissue was removed from the patient while ensuring no cancer cells were left behind.


Influences That Prevented the Acceptance of Mohs Surgery

The early-to mid-20th century was a time rife with cancer quackery as a variety of pills, potions and ointments were being touted as cancer cures and promoted widely. Born in rural Illinois in 1901, Harry Hoxsey was an ex-coal miner who defined himself as a healer in the 1920’s and was one such individual promoting these controversial cancer cures.[5] What was ill-fated for Dr. Mohs was one of Hoxsey’s treatments and Mohs’ paste both contained zinc chloride.[6] As a result, zinc chloride had largely been rejected by the medical community because of the horror stories associated with its use, particularly in Hoxsey’s clinics.[7] While there was certainly this larger dogmatic barrier due to the quackery association, there were also factors related to the technique itself that made it difficult for colleagues to accept. Surgeons at this time believed cutting into the tumour would to cause it to spread, so Mohs’ approach of removing the tumour piece by piece was thought to be dangerous for the patient.[8] The procedure itself also took days to complete and was painful for patients as Mohs would apply the zinc chloride paste (an escharotic agent) the day before surgery.[9] Mohs’ approach was so unlike the accepted procedures of surgical tumour removal that when other physicians saw the extensive erythema, edema, and purulence of the open slowly healing wounds, they thought their suspicions were confirmed.[10]


Circumstances that Lead to the Acceptance of Mohs Surgery

Today Mohs surgery is certainly not considered surgical quackery, nor is it considered a deviation from standards of surgical practice, but the eventual acceptance of Mohs surgery was a long process. The zinc chloride paste eventually disappeared as a barrier to the acceptance of Mohs surgery because there was a transition from the so called “fixed-tissue technique” (Mohs surgery with the zinc chloride paste) to a “fresh-tissue technique” (Mohs surgery without the use of the zinc chloride paste). This helped eliminate the association of Mohs surgery with the charlatan applying caustics to tumours. Mohs was originally targeting his research towards the attention of his surgical colleagues, but through various talks he gave during the 1940’s Mohs realized it was the dermatologists who were interested in his work. Theodore Tromovitch was a dermatologist and one of the first physicians to train with Mohs.[11] Tromovitch was instrumental in transitioning Mohs surgery from a fixed-tissue to fresh-tissue technique and reported great success in the early 1970’s performing Mohs surgery without the zinc chloride paste.[12] Not only were outcomes just as promising, but patients were even more grateful because of the decreased morbidity associated with the procedure. Tromovitch reported that his patients experienced significantly less pain as the zinc chloride paste was no longer applied to their skin the night before the surgery.[13]



Mohs considered himself an inventor, and based on the historical trajectory of Mohs surgery thus far I would argue that the real innovation here was the microscopic control, not the zinc chloride paste that caused so much resistance from Mohs’ colleagues.[14] Microscopic control referred to this idea of removing tissue in pieces, examining it under the microscope for the presence of cancer cells and then only returning to areas where cancer was present to remove additional tissue from the patient. This would ensure no cancer cells were left behind as this process was repeated until a cancer free plane was observed microscopically. It also ensured the least amount of tissue was removed from the patient as only areas with cancers cells present were excised further. Once the zinc chloride paste was removed from the procedure it became much easier for others to see the beauty of Mohs’ methodology, a transition which would not have occurred without the help of dermatologic colleagues.



[1] Randall K. Roegnigk and Henry H. Roenigk Jr., ed. Dermatologic Surgery Principles and Practice (New York, NY: Marcel Dekker, 1996), p. 703.

[2] Frederic E. Mohs, “Frederic E. Mohs MD,” Journal of the American Academy of Dermatology 9 (1983): p. 807.

[3] Frederic E. Mohs and Rachel Caruso, “Chemosurgery and Skin Cancer,” AORN Journal 13 (1971), 90.

[4] Ibid.

[5] Morris Fishbein, “History of Cancer Quackery,” Perspectives in Biology and Medicine 8 (1965): 157

[6] Dirk M. Elston, “Escharotic Agents, Fred Mohs and Harry Hoxsey,” Journal of the American Academy of Dermatology 53 (2005): p. 523.

[7] David G. Brodland, Amonette Rex, Hanke William and Perry Robbins. “The History and Evolution of Mohs Micrographic Surgery,” 26 (2000): p. 303.

[8] Ibid., p. 303

[9] Frederic E. Mohs, “Frederic E. Mohs MD,” Journal of the American Academy of Dermatology 9 (1983): p. 811.

[10] John A. Zitelli, “Mohs Surgery: Concepts and Misconceptions,” International Journal of Dermatology 24 (1985): p. 546.

[11] Frederic E. Mohs, “Frederic E. Mohs MD,” Journal of the American Academy of Dermatology 9 (1983): p. 810.

[12] Ibid., p. 811.

[13] David G. Brodland, Amonette Rex, Hanke William and Perry Robbins, “The History and Evolution of Mohs Micrographic Surgery,” 26 (2000): p. 304.

[14] Ibid., p. 305