How MOHS Procedure Works

Our surgeons remove the cancer layer by layer, examining each one microscopically until the margin around the cancer is free of cancer cells. This is a technically precise process in which the physician serves both as the surgeon and pathologist.

The Key steps in the procedure:

Surgical removal of the skin cancer is performed.

  1. The surgical site is washed and a local anesthesia is injected into the surgery site.
  2. Fine surgical instruments are used to remove the visible cancer. Often times this is done by scraping because cancer cells are softer in texture than your normal skin and scrape away easily.
  3. A thin layer of normal appearing skin surrounding the tumor is removed in hopes of getting a “cancer free” margin. This Is generally only 1-2mm around the tumor.
  4. A map is drawn of the tissue specimen that was removed from the patient.

The tissue is processed for approximately one hour while the patient waits in our waiting room.

  1. The tissue is dyed different colors to orient top to bottom and left to right. This is recorded on the map.
  2. The tissue is frozen and cut into thin pieces 1/10 the thickness of a piece of paper.
  3. The thin pieces of tissue are placed on slides and dyed a second time so the cancer cells are visible under the microscope.

The entire undersurface and skin edges of the removed tissue are evaluated microscopically by a physician.

  1. The physician looks at the slides and determines if the cancer has been completely removed.
  2. If cancer remains, the physician marks on the map where the tumor is still present.

If any skin cancer remains, more tissue is removed using the map as a guide. The tissue is processed and examined under the microscope.

  1. Due to the “mapping” technique, the doctor is able to remove only the cancer and preserve healthy tissue keeping the wound as small as possible.

To Make An Appointment Call (425) 672-1333

MOHS Surgery Procedure Puget Sound Dermatology
MOHS Surgery Procedure Puget Sound Dermatology


Once the cancer is completely removed, reconstruction to give the best cosmetic outcome of the affected area is performed

  • There are several reconstruction techniques depending on the size and location of the wound. A small simple wound may be allowed to heal on its own. A slightly larger wound may be closed with stitches, Larger wounds may require a skin graft or flap.
  • The size of the scar depends on the size of the tumor. It is often difficult to predict the size of the tumor prior to surgery.
  • Mohs surgeons are highly trained in reconstruction techniques and we perform 99% of the Mohs reconstructions in our office. However, in certain circumstances, a defect may become too large or invasive for us to properly close the wound. In order to best take care of the patient a specialized surgeon may be used to assist with reconstruction.

Meet Our Providers

Our providers continue to maintain the highest levels of accreditation and progressive ongoing education to learn and understand the latest developments in medical dermatology. Each provider's education and bio can be viewed below.


Melanie Kuechle, MD

Dr. Kuechle is a native of Texas and a graduate of Baylor University College of Medicine. She completed her dermatology residency at...


Dr. Craig Birkby

Dr. Birkby is Board Certified by the American Board of Dermatology and has performed over 15,000 Mohs surgeries...

Dr. Nguyen Sheena Puget Sound Dermatology

Sheena Nguyen, DO

Dr. Nguyen is a Fellow of the American Academy of Dermatology and a Board Certified, Fellowship-trained Pediatric Dermatologist. She was born and raised...


Ame Phitwong, ARNP

Ame is a board certified Adult-Gerontology Primary Care Nurse Practitioner who has worked entirely...