1. From General Surgery to Dermatology : A Historical Perspective of Mohs Micrographic Surgery By: Patricia Ting, BSc, University of Calgary & Anatoli Freiman, MD, McGill University

2. Mohs Micrographic Surgery Uses: cutaneous tumours Indications: indeterminate tumour borders, recurrence with other treatment modalities, facial lesions (ex. nasolabial folds, eyelids, ears, etc) Maximum cure rates –>98% for basal & squamous cell carcinoma Maximum sparing normal tissue Revolutionized dermatologic surgery

3. Dr. Frederic E. Mohs Frederic E. Mohs was born in 1910 1933: Mohs was medical student at the University of Wisconsin He worked as an assistant in a cancer research laboratory, investigating the effect of various irritants on implanted cancers in rats

4. Zinc Chloride Injections of 20% zinc chloride effectively and accurately penetrated the tissues without systemic toxicity. The chemical was also safe to handle, as it did not diffuse into the keratin layer of the skin, unless a keratolytic, such as dichloroacetic acid, was previously applied.

5. Histological Preservation Most importantly, this zinc preparation maintained the histologic architecture of these tissues. Mohs subsequently proposed the concept of chemical fixation followed by surgical excision of tumours with microscopic examination of tumour margins. Thus, the concept of micrographic chemosurgery was born.

6. Dr. Frederic Mohs was originally trained as a general surgeon 1936: began treating patients with cutaneous malignancies at the Wisconsin General Hospital

7. Original Mohs Procedure Step 1: Injection of local anesthetic Step 2: Application of in-situ fixative Ingredients: –Saturated zinc chloride solution –Stibinite – antimony ore (granular matrix) –Sanguinaria canadenis (binder for ZnCl) Step 3: In vivo fixation with zinc chloride paste for 12 to 24 hours

8. Step 4: Surgical excision of tumour in saucer-like horizontal sections Allows for entire base and margins of defect to be examined

9. Step 5: Horizontal sections are frozen & stained Step 6: Microscopic examination of frozen sections

10. Residual neoplastic tissue: Reapplication of the in vivo fixative for 24 hours Further serial removal of affected tissues

11. The process of fixation, surgical excision and microscopic examination was repeated until the margins were clear. Defects were allowed to healed by secondary intention as the in vivo fixative sloughed over the course of 7 to 10 days. If required, skin grafts were performed after this time period.

12. Ink Dyes Mohs subsequently refined his technique by color-coding the specimen edges with –Red (merbromin) –Blue (laundry dye) –Black (India ink) The addition of ink dyes provided a precise reference map of the tumour to be drawn and juxtaposed upon the corresponding surgical wound bed

13. Rejection of Mohs Technique Initially, Mohs’ pioneering surgical concept was not well accepted by the surgical community. Several concerns with the procedure: 1.Patients complained of extreme pain due to the caustic effects of ZnCl fixative, which induced edema and tissue necrosis 2. Local inflammation made it difficult to interpret tumour histopathology

14. 3. Extremely labor intensive to microscopically examine the tumour and repeat process for incompletely excised margins 4. Increased infection rates due to delayed surgical reconstruction and closure of wound bed/defect 5. Belief that cutting through the tumour would promote local seeding of tumour cells and metastatic spread Therefore, surgeons at the time preferred conventional wide margins for the removal of cutaneous tumours

15. Dr. Erwin Schmidt While the general surgical community did not support Mohs’ technique, several surgeons at the Wisconsin General Hospital continued to use the procedure 1940s: Mohs’ clinic was transferred to the Department of Surgery where a supportive chief, Dr. Erwin Schmidt, prepared a forward for the first clinical article about Mohs’ technique in the Archives of Surgery

16. American Academy of Dermatology (1946) Mohs’ technique caught the attention and interest of dermatologists who recognized the useful applications of this procedure Soon after, many dermatologists from around the world came to observe and train with Dr. Fredric Mohs at the University of Wisconsin

17. Dr. Ray Allington 1951: suggested that dichloroacetic acid could be used for hemostasis after the debulking procedure 1953: an instructional documentary was filmed to demonstrate this modification on a multistage removal of an eyelid basal cell carcinoma

18. Fresh Tissue Technique Due to the time constraints of the filming session, Mohs injected the residual tumour with local anesthetic and omitted the second round of ZnCl fixation Observation: histologic resolution of the tumour margins was not significantly impeded without in vivo fixation This new technique was also illustrated in the 1 st edition of Epstein’s Skin Surgery (1956)

19. Advantages to the Fresh Tissue Technique No tissue inflammation & sloughing More tissue conservation Same day reconstruction of the defect The real reason for the success of the Mohs technique was not the chemical fixation of the tissue, but the microscopic control.

20. American College of Chemotherapy 1960s: Mohs’ technique gained widespread acceptance, eventually leading to the development of the American College of Chemotherapy 1970: Dr. Theodore Tromovitch, who had been using the fresh tissue technique since the 1960s, presented a case series of 75 patients treated for cutaneous carcinomas and reported high cure rates with this new technique

21. American College of Mohs Micrographic Surgery and Cutaneous Oncology (ACMMSCO) 1986: establishment of the ACMMSCO officially regulated the minimum one year fellowships in Mohs Micrographic Surgery Mohs fellowship requires specialized training in a composite of skills including dermatopathology and reconstructive surgery

22. Modern Day Mohs Procedure High-tech cryomachines for preparation of frozen sections

23. Lab technicians stain the frozen sections in a series of cellular dyes

24. Electrocautery is used to control the bleeding Same day reconstruction of the wound bed/ defect

25. Timeline of Events 19331936194819531970 19301940196019501970 12 years17 years Original concept Fresh Tissue Technique Use for cutaneous carcinomas

26. Conclusion Examination of 100% of tumour margins Maximal sparing of normal tissues Provides excellent cosmetic results Cure rates after Mohs is > 98% for SCC, BCC Today, it is considered one of the greatest contributions in the newly evolving field of dermatologic surgery.

27. In the words of Dr. Fredrick Mohs (1910-2000) “Winning acceptance takes much patience.”

28. Acknowledgements Dr. Anatoli Freiman (Montreal, QC) Dr. Lawrence Warshawski (Vancouver, BC) Dr. Dan Issen (Irvine, CA) Dr. David Zloty (Vancouver, BC) Dr. John Arlette (Calgary, AB)