Mohs surgery is a procedure primarily indicated for treatment
of locally invasive cancers with high-risk of recurrence.
Named after Frederic Mohs, the general surgeon who invented the procedure in the 1930s,
Mohs surgery is done in a series of stages
to achieve a cancer-free margin while preserving a maximal amount of unaffected tissue.
This video will cover the surgical process by following two patients through their stages
of surgery for basal cell carcinoma and closure.
A stage is defined as each round of skin layer resection, processing of the layer onto slides,
and histology review and confirming presence
of remaining cancer or achievement of clear margins.
To obtain clear margins, patients may undergo more than 1 stage of Mohs surgery,
with the average being about 1.6 for early stage cancers.
Once the patients are consulted and prepared for their respective surgeries,
their surgical sites are marked and confirmed.
Patient 1's cancer is just in front of the ear,
while Patient 2's cancer is located closer to the temple.
The skin is prepared with an antiseptic skin cleanser.
Patients are awake during this procedure, so a local anesthesia is injected
to ensure the surgical area is numbed.
The cancer can be debulked with a curette or scalpel.
The size of the layer removed depends on the type of cancer.
At a minimum, it must be wider and deeper than the biopsy.
Before removing the first layer, the surgeon takes caution
to maintain the layer's orientation relative to the surgical site.
Mohs surgeon preferences for maintaining orientation may differ.
They may use reference marks around the surgical site at 12, 3, 6,
and 9 o'clock to maintain orientation, or in this case, the surgeon marks a piece
of paper denoting the top of the patient's head.
The main thing is that all members of the Mohs surgical team are trained
to understand the conventions.
The surgeon has divided the layer down the middle to make processing
and visualizing margins easier when it moves to histology.
Cautery is used to stop any bleeding that occurs during the surgery.
The patient is given a pressure bandage and can proceed
to a waiting area while the first layer is taken to a nearby histology lab for processing
by a Mohs trained histotechnician.
The removed skin can be processed whole or, as seen here,
divided and processed as smaller pieces.
A diagram, or Mohs map, is created by recording the orientation of the layer.
This Mohs map can be either drawn, or based on a photograph.
Cut pieces and any colored inks used to highlight the orientation
of the samples are recorded on this Mohs map.
Again, conventions differ between surgeons and teams, so those demonstrated
in this video are conventions understood by every member of the team.
The histotech embeds the color marked skin on a slide to ensure
that all margins are aligned on the same plane.
Once it is frozen into a block, 4 to 5 sections at about 4-6 microns thick,
are taken from each piece and collected on a slide for staining.
Haematoxylin and eosin staining takes about 30 minutes before it is ready for review
by the surgeon under a microscope.
The surgeon reviews the sections on the slide for any signs of cancer
that are small, hidden, or deep under the skin.
Under H&E staining, basal cell carcinomas will stain bluer due to their larger nucleus
and higher nuclear to cytoplasmic ratio.
Piece 1's surgical margins look free of cancer.
Looking at piece 2, the surgical margins also look free of cancer.
The good news for patient 1 is that the margins are clear of cancer in 1 stage of Mohs surgery.
The surgeon will mark this on the map
and have the patient return to the room for wound closure.
Discussion with the patient on closure can be done during a consultation visit,
before surgery, or after margins are clear.
Most Mohs surgeons will close the wound the same day as the surgery in a linear fashion.
In some circumstances, more extensive surgery may be necessary to repair the wound.
Examples include a skin graft, a flap, or a multi-step procedure where more
than one surgery is required to complete the process of fixing the wound.
A Mohs surgeon may also partner with another surgical specialist
to close the wound, often on a separate day.
To facilitate the best healing outcome and minimize scaring, more areas of skin are cut
to create a linear closure along skin-tension lines.
This helps create a better, more aesthetic repair, since an irregular wound being closed
in a line would cause raised areas that don't lie flat.
The surgeon repairs the skin with a dissolving buried vertical mattress suture,
before finishing with a non-dissolving simple running suture.
The patient is instructed on wound care by the Mohs surgeon
and the non-dissolving suture will be removed during a follow-up visit.
Now let's return to our second patient's stage 1 results.
The Mohs surgeon has found remaining cancer on both sides of the stage 1 layer margins.
Bluer stained cancer can be seen in piece 1 of layer 1
between the epidermal and dermal layer of the margin.
And in piece 2 of layer 1, we can see the cancer along the margin noted in these areas.
The surgeon now marks the locations to return to on the Mohs map as references for stage 2.
The patient is called to return to the clinic room and consulted on areas
that will be removed for stage 2.
The surgery then proceeds as outlined previously, with the difference being
that only the marked areas with cancer are removed.
Returning to the microscope after the stage 2 layer is prepared,
we can see that piece 1 of the layer is free of cancer.
However, the other piece of the layer still has remaining cancer in the margin.
The surgeon marks the results on the stage 2 map as reference for stage 3.
The patient returns to the clinic room to remove stage 3's layer in the area
where cancer was seen on the margin.
Upon review of stage 3's layer, we can see that the margin is now free of cancer.
The Mohs surgeon notes this on the map and can now proceed to wound closure for patient 2.
Similar to patient 1, the surgeon marks additional areas of skin removal to allow
for closure along skin-tension lines.
Scars are typically raised and pink during their initial healing.
They will improve on their own and continue to mature and improve over several months.
Mohs surgeons undergo specialized training to perform the procedure effectively.
Learn more about Mohs surgery online at JAMA Dermatology.com