How did it get its name?

The concept was first developed by Dr. Fredrick Mohs in the 1930s.  Since that time a great number of gifted surgeons have contributed to the refinement and improvement of this original technique.  However, it still rightfully carries the name of its founder.  The technique involves removing a small sample of skin around a skin cancer.  This is taken in the shape of a lens to allow for proper processing.  The tissue is then frozen to -24 degrees and cut into sections as thin as a few micrometers.

Why Mohs Surgery?

It is the most effective and advanced treatment for skin cancer.  There are three main benefits:

1.  It offers the highest cure rate.

  •  When performed by an expert, cure rates reach 99% for the most common skin cancers.  That means there is a 99% chance your cancer has been completely removed and will not come back.  This is a 5-15% improved cure rate over any other method.
  • Those whose cancer returns after another type of skin cancer removal surgery have a lower cure rate.  However, cure rates for this population remain as high as 95% with Mohs surgery.  This is far superior to any other type of surgery.
  • Mohs can offer such high cure rates because it looks at 100% of the edge while standard biopsy processing looks at only 4-10% of the edge. 

2.  It leaves the smallest wound possible.

  • Traditional excision removes a “standard margin” which involves marking the visible edges of the skin cancer.  A mark ranging from 4mm up to 2cm is then made on each side around the skin cancer.  The edges then have to be extended to allow the skin to close correctly




  • During the Mohs procedure the visible edges are also marked, but only 1-2mm are taken beyond those.  If needed, additional layers measuring one to two millimeters in size are taken.  Although, additional layers are only taken where the roots of the skin cancer were seen. 

3.  The entire procedure is performed in one day.

  • Since the skin cancer is examined under the microscope during the surgery there is no waiting on the final pathology results. 
  • If a traditional excision is performed and the tissue that was removed still has cancer in the edges another surgery will be needed.  During Mohs the edges are checked while the surgery is being performed so a second surgery is never needed for this reason.

How Mohs Works

Step 1

 The roots of a skin cancer may extend beyond the visible portion of the tumor. If these roots are not removed, the cancer will recur. 

Step 2

The visible tumor is surgically removed.

Step 3

A layer of skin is removed and divided into sections. The ACMS surgeon then color codes each of these sections with dyes and makes reference marks on the skin to show the source of these sections. A map of the surgical site is then drawn.

Step 4

The undersurface and edges of each section are microscopically examined for evidence of remaining

Step 5

If cancer cells are found under the microscope, the ACMS surgeon marks their location onto the "map" and returns to the patient to remove another layer of skin - but only from precisely where the cancer cells remain.

Step 6

The removal process stops when there is no longer any evidence of cancer remaining in the surgical site. Because Mohs surgey removes only tissue containing cancer, it ensures that the maximum amount of healthy tissue is kept intact.  Reconstruction is now performed.

step images borrowed from the american college of mohs surgeons

Why Mohs Surgery?