MOHS MICROGRAPHIC SURGERY (MMS)

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MOHS MICROGRAPHIC SURGERY (MMS)

• Hayleigh Gordon Histology BMS 1

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What is MOHs ?

• Mohs surgery or MMS is a specialised technique
  enabling the surgeon to remove a skin tumour in
  several stages. Without removing too much healthy
  tissue.
• Technique was pioneered by Fredrick Moh, an
  American Surgeon in the late 1940s.
• It is called micrographic surgery as each piece
  of skin removed is checked and examines using a
  microscope.

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• All Kent MOH skin procedures take place at
  Canterbury Hospital, this is a very specialist
  surgery and is only available in a few hospitals
  within the UK.
• There are two surgery procedure rooms, both with
  quick access to the moh room

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WHY USE MOHS?

• Mohs micrographic surgery is commonly used to
  remove large tumours, tumours in hard to treat
  places as well as recurrent tumours.
• It is commonly used on Basel Cell Carcinomas
  (BCC), it can be also be used on Squamous Cell
  Carcinomas (SCC) as well as Melanomas in some
  cases.

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What is a BCC?

• Basal cell Carcinomas are the most common cancer
  found in humans.
• It arises from the basal cell layer of the skin,
  in the majority of cases it grows slowly.
• Fortunately these tumours virtually never spread
  internally or present life threatening. They can
  however grow to be unsightly, or cause facial
  distortion.
• Most cases of BCC are related to exposure to
  sunlight or repetitive sunburn injury. There are
  however a few genetic disorders such as Gorlins
  syndrome which lead to a tendency to develop
  BCCs.

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Overview of Moh surgery
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Mohs surgery cont

• The removed tissue is carefully mapped on a
  schematic drawing.
• The tissue is colour coded using different tissue
  marking paints to identify the different margins.

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Moh surgery cont

• Once inked the tissue is flattened as much as
  possible to ensure the whole tissue margins can
  be cut and seen when stained.
• A chuck is covered in OCT, a medium to hold the
  tissue securely. The tissue is added onto the
  chuck an placed into a widget. The widget is
  linked to a liquid nitrogen canister, which is
  controlled by a foot pedal. Whilst pressing this,
  the surgeon flattens the tissue. The liquid
  nitrogen freezes the surrounding medium and the
  tissue, holding it securely in place.

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Equipment
Liquid nitrogen canister
Widget
Foot pedal attachment
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Mohs procedure

• The frozen chuck is then given to the Moh
  assistant to be placed into the Cryostat.
• Tissue is cut quickly and efficiently.
• The surgeon may perform 3- 4 patient procedures
  in short succession, the assistant must keep the
  chucks in order with clear patient
  identification.

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Cryostat
Temperature monitor
External wheel for movement, enabling Efficient
cutting of a section
Tools (kept cold)
Storage for chucks
Chuck holder
Blade
Controls thickness Of sections in micrometres .
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Cryostat

• A cryostat is a microtome within a freezer,
  sections are cut at a certain temperate usually
  between -20 and -30 Celsius.
• Once frozen, the specimen on the chuck is mounted
  on the microtome. The external wheel is rotated
  and the specimen advances toward the cutting
  blade. Once the specimen is cut to a show full
  face therefore the whole section can be seen
  including a full epidermis, it is mounted on a
  warm (room temperature) clear glass slide, where
  it will instantaneously melt and adhere. These
  can then be placed onto the linear strainer.

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Staining

• A Haematoxylin and Eosin stain is used to aid
  medical diagnosis. Haematoxylin stains nuclei of
  cells blue, eosin is the counter stain which
  stains the other structures various shades of red
  or pink.
• As the sections are cut they are placed on a
  liner stainer, this is quicker than a routine use
  laboratory stainer. It takes 10-15 minutes to
  travel through the required solutions.

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Liner Stainer
Bicycle chain to attach slide holder
Eosin
Haematoxylin
Alcohol
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Mohs procedure cont
Stained section on slides
Microscopic View
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Mohs procedure

• Once the slides have been efficiently stained
  they are held within a xylene bath. The slides
  are then removed and quickly cover slipped. They
  are placed within slide trays in order.
• They are placed by the microscope for rapid
  diagnosis. The surgeon thoroughly examines the
  slide microscopically. 100 of the tissue margin
  is examined and evaluated, to ensure whole tumour
  removal. If cancer cells are seen the area is
  marked on the schematic drawing and the process
  is repeated after removal of more tissue from the
  patient.

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Microscope
Lens
Main microscope view
Second lens
Slide camera
objective
Slide platform
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Moh Benefits

• The process is designed to be quick for rapid and
  effective removal. The surgeon will remove skin
  until they are confident there is no tumour left
  behind.
• For certain skin cancers Mohs procedures have a
  cure rate of up to 99. It is precise while
  sparing of healthy tissue. Therefore scarring is
  kept minimal also.
• The procedure enables you to go home the same day
  as your operation, providing everything goes to
  plan

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Moh Risks

• As with any surgery there is always risk. However
  with the lowest recurrence rate it is seen to be
  extremely beneficial.
• The procedure can be lengthy and is performed
  under local anaesthetic which carries its own
  risks to each patient.

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Any questions???????