Re:Mohs technique

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From:"MICHAEL BECKER" <> (by way of histonet)
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In response to Barbara Chapman's inquiry about Mohs.  Mohs was actually a
person before a technique. Dr. Frederick Mohs began development of the Mohs
surgical technique for the removal of skin cancers as a med. student back
in the 1940's I believe.  Since then the technique has been modified. Dr.
Mohs developed a procedure whereby instead of taking a large surgical
margin of skin and subcut. tissue he only removed what showed cancer
microscopically.  He started this by using a fixative paste that was put on
the skin. It fixed the tissue in situ and was removed later and processed
by a histologic technician.  Over the years his technique changed and the
name changed.  Initially it as Mohs-fixed tissue method. This method was
very time consuming and painful for the patient.  Over time it was
modified.  The paste was eliminated entirely and fresh tissue was then
excised in a precise way so as not to take more than was necessary.
Currently it is called Mohs Micrographic Surgery.  Mohs invented it, it is
done with an anatomic map and microscope and it is a surgery

When a Mohs surgeon does this procedure he/she draws a simple map of the
site being done usually on the face so he can orient each piece of tissue
to that map as each stage of the procedure is done.  Usually pathology
breadloaves an elliptical excision of skin vertically or 90 degrees to the
surface of the skin and embeds each slice horizontally so the skin is shown
from epidermal edge to deeper margin edge.  This would be chemically
processed and infiltrated with paraffin.  That would take a few days at
best with processing, slide prep and reading the slides out.  With Mohs
your surgeon is also your clinician and the doctor reading the skin cancer
slides at the time of surgery.  The specimen is not taken as a wide excison
instead smaller portions of skin are take and processed as the patient
waits.  Instead of breadloaving the specimen is oriented such that the
whole epidermal margin can be laid flat against a glass slide.  It would be
analogous to taking a shave of skin whole with the cut surface down and
placing it directly on a flat surface in order to embed it.  Your "mold" is
the glass slide.  Once all the skin edges are teased flat OCT embedding
media is placed on top of it and a separate metal chuck (For frozens) the
slide with frozen tissue is then inverted-flipped over and place on the
metal chuck. The glass slide is warmed and removed.  Then you have the flat
cut surface of tissue that represents the true margin from the patient.
This is cut and stained and if there is skin cancer still present the Mohs
surgeon will see it and go back and take more tissue until no cancer
remains.  In the practice I work in this can take anywhere from 2 to 4
hours or more depending on the extent in infiltration and the cancer type
BCC basal cell vs squamous cell.  The map allows the doctor to accurately
pinpoint where andy cancer cells remain and tells him where to take more
tissue from.  The cure rate for BCC's is almost 100%.  I am not sure about
SCCs.  Since skin cancer occurs mostly on the face, scalp, necka and ear
areas it is crucial to conserve tissue.  This is for cosmetic as well as
functional concerns.

I hope I answered your question.  Mohs histotechnology is in its infacny.
I have been doing this for about 2 yrs.  There are many articles out there
in journals like Derm. Surgery, etc.  Mohs wrote some and then his students
also have contributed.  The technique has an interesting evolution from
1940's to the present.

Are you about to do this type of histology or were you just curious??

Sue Becker, HTL
Dr. Michael J. Mulvaney
Private practice
Albany, NY

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