How MOHS Micrographic Surgery is done

Mohs skin cancer surgery is routinely performed in four stages. Mohs surgery may take hours to complete due to the methodical and precise manner in which the surgery is performed.

In the first stage of the Mohs skin cancer surgery, a local anesthetic is injected in the area that is to be treated after it has been cleaned and the potentially cancerous area marked. Any visible skin cancer is removed and then a thin layer of additional tissue is removed. This part of the surgery is usually quick, only lasting for several minutes.

A diagram is then made of the removed tissue specimen after it has been cut into sections and stained. The tissue is frozen using a cryostat and thin slices are removed from the edge of the specimen and from the undersurface. Each of these slices of tissue are put on slides and stained. This part of the procedure takes the most time and may take over one hour to complete.

During the second stage of the Mohs skin cancer surgery, the doctor examines each tissue slice under the microscope. The goal is to accurately identify all microscopic "roots" of the cancer and then locate them precisely on the Mohs map or diagram. The physician will be looking for any residual cancer in the tissue slices. If any residual cancer is found, The physician will use the Mohs map as an aid in removing any necessary additional tissue.

Stage three of the Mohs surgery is simply a repeat of the second stage. This process is continued until all tissue specimens are free of residual cancer cells.

The fourth stage is the repair of the surgical defect. The size of the surgical defect will vary depending upon the size of the cancer under the skin. Some cancers are much larger under the surface than they appear. Removal of cartilage or bone may be needed and may result in a fairly large surgical defect.

Patients should expect to spend a good part of their day at the doctors office or outpatient surgery center. The surgeon will not be able to predict the time needed to perform the surgery nor the size of the surgical defect before the second and third stages of the surgery are completed.

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