Skin Cancer: What Is Mohs Surgery?

Medically Reviewed

If you basked in the sun when you were younger, you may be paying the price for that exposure as you grow older. Research reports that one in five Americans will eventually develop skin cancer.

Most people are likely to develop basal cell or squamous cell carcinomas. Both are often grouped as nonmelanoma skin cancers. This distinguishes them from the most dangerous type of skin cancer, melanoma.

Nonmelanoma skin cancers carry a lower risk of metastasizing (spreading to distant parts of the body) than melanoma. Though slow growing and rarely life-threatening, nonmelanoma skin cancers can cause disfigurement and metastasize if left untreated.

Nonmelanoma skin cancers often begin as a small bump or tender area that may bleed and/or scale or crust. Although skin cancers can develop anywhere, most occur in sun-exposed areas such as the face.

According to an analysis published in the April 2012 Archives of Dermatology, a growing number of Medicare patients are undergoing surgery to treat nonmelanoma skin cancers, which are typically associated with accumulated exposure to ultraviolet rays from the sun.

Nonmelanoma skin cancers can be treated in a variety of ways. Your doctor will choose the best option based on your tumor’s size, location, and growth pattern. Standard forms of treatment include:

Conventional excisional surgery

Scraping and burning

Radiation therapy

Cryotherapy (freezing and destroying)

Topical medication, such as imiquimod

Another procedure, called Mohs micrographic surgery, is being used more and more, particularly to treat skin cancers on the face.

Mohs surgery has a high cure rate and preserves more healthy, noncancer-containing tissue. It can leave a smaller defect and, subsequently, a smaller scar.

How Mohs works

Mohs surgery is named after Frederic E. Mohs, M.D., the surgeon who developed the original technique in the 1930s. It is used predominantly to treat facial lesions, especially those on the lips and eyelids, where tissue preservation is critical. Mohs also has a high cure rate in treating recurring nonmelanoma skin cancers.

Not everyone is a candidate for Mohs surgery. Having other health conditions may preclude some people from undergoing the procedure, especially patients ages 85 and older. Also, undergoing the faster excision surgery instead of the lengthy Mohs procedure may be more practical for elderly patients.

The Mohs technique is a specialized outpatient procedure using local anesthesia performed by a doctor who has been trained to act as both surgeon and pathologist (an expert in analyzing tissue). Mohs also requires a specialized technician and laboratory to process the tissue.

You are awake during the surgery, and the surgical site is locally anesthetized. The Mohs surgeon removes your tumor in layers and examines each layer under a microscope to look for remaining evidence of cancer. (The lab work takes about an hour.)

If the surgeon finds any portion of the tumor remaining, he or she removes additional layers, repeating the process until the cancer is absent. The entire procedure typically lasts two to four hours and sometimes longer depending on the extent of cancer. The surgeon typically removes one to four layers.

Once the cancer has been completely removed, the defect can be reconstructed, often on the same day.

Wound reconstruction

After the cancer is removed, your Mohs surgeon can choose from a number of options when deciding how to repair the defect. They range from simple—the defect is allowed to heal on its own over the following weeks—to very complicated—a series of surgical procedures are performed.

Many Mohs surgeons are specially trained to perform both Mohs excision and repair. Sometimes, however, depending on the defect’s size and location, other specialists may be called on to complete reconstruction.

Your doctor may give you pain relievers to ease any discomfort from the surgery and/or oral antibiotics to prevent infection immediately after the procedure. Mohs surgical complications are rare but can include excessive bleeding, nerve damage, infection, wound reopening, and formation of a keloid (a tough, raised scar) at the surgical site.


As with any type of surgery, Mohs leaves some degree of scarring. As your wound heals, you can expect to see firm scar tissue and some discoloration. All scars soften and improve with time, but it may take months to a year or more for the scar to heal completely.

Some patients may need additional procedures such as sanding, laser treatment, or injections for the scar to look its best. Be sure to talk with your doctor before your surgery about your expectations, including wound-healing, scarring, and post-operative care issues.

You’ll need to visit your doctor for regular checkups. Once you’ve had skin cancer, you’re at a higher risk for developing it again.

In fact, 40 percent of patients who’ve had a basal cell carcinoma develop another one within five years, so it's important to watch for new lesions and visit your doctor regularly.

And of course, adopt safe sun practices, such as wearing lip balm and sunscreen with a sun protection factor (SPF) of at least 30.

Learn more about the most serious form of skin cancer, melanoma, and how to prevent it.