Mohs Micrographic Surgery: What it is and What to Expect

Mohs Micrographic Surgery: What it is and What to Expect

by: Megan Shelton, MD

Skin cancer is the most common form of cancer in the United States, with about one in five Americans developing it during their lifetime. Fortunately, most cases of skin cancer are curable when diagnosed and treated promptly. While there are many approaches to treat skin cancer, Mohs micrographic surgery offers the highest cure rate for skin cancers located in areas where the preservation of healthy tissue is important for maximum functional and cosmetic results. 

In this blog post, we will discuss what Mohs surgery is, what to expect during and after the procedure, and how to prepare for it.

What is Mohs Surgery? Mohs micrographic surgery is a specialized technique used in the removal of skin cancer that combines surgery with microscopic margin analysis. It is most commonly used to treat basal cell carcinoma and squamous cell carcinoma. Over time, as skin cancer grows, cancerous cells spread deeper into the skin, similar to the roots of a tree. These skin cancer ‘roots’ are only visible under the microscope and cannot be identified with the naked eye. Fortunately, Mohs surgery allows for the precise identification and removal of cancerous cells while minimizing damage to the surrounding normal skin.

During Mohs micrographic surgery, cancerous tissues are removed as a disc or ‘layer’ along with a thin margin of normal tissue. Once this tissue is removed, the edges are precisely marked with colored dyes and a corresponding map of the tissue is created. A technician processes and freezes the tissue in the Mohs laboratory and creates microscope slides. The surgeon then examines the slides under the microscope and evaluates all of the margins for residual tumor. If cancer ‘roots’ remain at the outer edges of the excised tissue, an additional ‘layer’ of tissue will be removed from only the involved areas. These steps are repeated until all edges are cleared of cancer. 

Because the margins are evaluated microscopically for skin cancer, Mohs surgery provides extremely high cure rates for skin cancers. Additionally, loss of healthy tissues is minimized. 

After the skin cancer has been successfully removed, the Mohs surgeon will assess the wound and discuss options for healing, taking into account functionality and final cosmetic appearance. If reconstruction is necessary, the wound is typically repaired the same day as the tumor removal. 

What to Expect During Mohs Surgery? Mohs surgery is an outpatient procedure performed in the clinic under local anesthesia. Surgery typically begins early in the morning and is completed the same day. The length of the procedure can vary depending on the number of stages needed to remove the skin cancer and the extent of reconstruction required. While it is impossible to predict exactly what timeframe to expect for each Mohs surgery procedure, the entire procedure usually lasts several hours.

Patients are advised to wear comfortable clothing. In most cases, patients are allowed to eat, drink, and take all medications on the day of the procedure. 

After reviewing the procedure and consent form, the surgery site is identified together with the surgeon. Local anesthesia is administered in order to numb the surgery site, similar to the initial biopsy. Patients are awake and comfortable during the entire procedure. After the site is anesthetized, it typically only takes a few minutes to remove the skin cancer. Once the first ‘stage’ is completed, a bandage is placed over the wound while waiting for the results. It takes approximately one hour for the tissue to be processed and examined. If any cancer is identified at the margins, the area is re-anesthetized and additional ‘layers’ of tissue are removed until all edges are cleared of cancer. The majority of tumors are removed in one to three ‘stages’, though occasionally more are required. 

Once the skin cancer has been successfully removed, the Mohs surgeon will assess the wound and discuss options for healing. Some wounds are allowed to heal on their own, while others require suturing. Before leaving, a pressure bandage is applied to the surgery site and wound care is reviewed.

After Mohs Surgery. The recovery after Mohs micrographic surgery is straightforward in most cases. Occasionally, patients may experience mild postoperative discomfort, swelling, bleeding, or redness at the surgery site, though these symptoms generally resolve quickly. 

Patients will need to take care of their wound as they recover, and specific wound care instructions will be provided by the Mohs surgeon. Typically wound dressings are changed daily. It is very important to avoid strenuous activities and exercise during the recovery period in order to optimize healing and avoid postoperative complications. 

Once the external sutures are removed, the scar may remain pink for months but will fade with time. While a scar will always remain at the surgical site, protecting the scar from the sun with sunscreen will help minimize its appearance. Generally, the appearance of a post-surgical scar improves with time, fully maturing after one year or more. Occasionally, additional procedures may be needed to improve the scar. 

After an initial skin cancer diagnosis, patients are at increased risk of developing skin cancer at other sites on their skin. Thus, patients should continue regular skin cancer screenings with their dermatologist, and monitor their skin closely for any new or changing lesions. 

Preparing for Mohs Surgery. Patients may meet with a Mohs surgeon at a preoperative consultation to discuss treatment or reconstructive options. Patients should disclose any underlying health issues, such as heart disease and high blood pressure. They should also let their surgeon know all the prescriptions and supplements they are taking to avoid any risks or complications.  In most cases, all medications are continued during the procedure and in the postoperative period. Patients should also consider temporarily stopping smoking or using tobacco products due to delays in wound healing.

Meet Megan Shelton, MD

Meet our author, Megan Shelton, MD, a dermatologist and Mohs surgeon specializing in skin cancer treatment at Sanova Dermatology in Central Austin. With a focus on compassionate care, she earned her medical degree from the University of Texas, completed her residency at Dell Medical School, and pursued fellowship training at the University of Michigan. Dr. Shelton is dedicated to patient education and has authored numerous publications. To schedule your visit with her, click here.


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