Transcript A Historical Perspective of Mohs Micrographic Surgery

From General Surgery to Dermatology:
A Historical Perspective of
Mohs Micrographic Surgery
By:
Patricia Ting, BSc, University of Calgary
&
Anatoli Freiman, MD, McGill University
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
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
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.
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.
• Dr. Frederic Mohs
was originally trained
as a general surgeon
• 1936: began treating
patients with
cutaneous
malignancies at the
Wisconsin General
Hospital
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
Step 4:
Surgical excision of
tumour in saucer-like
horizontal sections
Allows for entire base
and margins of
defect to be
examined
Step 5:
Horizontal sections
are frozen &
stained
Step 6:
Microscopic
examination of
frozen sections
Residual neoplastic
tissue:
• Reapplication of the
in vivo fixative for
24 hours
• Further serial
removal of affected
tissues
•
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.
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
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
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
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
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
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
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 1st edition
of Epstein’s Skin Surgery (1956)
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.
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
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
Modern Day Mohs
Procedure
• High-tech cryomachines for preparation
of frozen sections
• Lab technicians
stain the frozen
sections in a series
of cellular dyes
• Electrocautery is
used to control
the bleeding
• Same day
reconstruction of
the wound bed/
defect
Timeline of Events
Original
concept
Fresh Tissue
Technique
1933 1936
1948
Use for cutaneous
carcinomas
1953
12 years
1930
1940
1970
17 years
1950
1960
1970
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.
In the words of Dr. Fredrick Mohs
(1910-2000)
“Winning acceptance takes much patience.”
Acknowledgements
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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)