Mohs Surgery: How Many Stages Will Be Required?

Written by Jessica “Nikki” Dietert, MD, Board Certified Dermatologist on February 14, 2023 One Comment

mohs surgery recovery

Mohs surgery is a type of skin cancer surgery that is named for Frederic Mohs, the dermatologist and researcher who invented the practice in the 1930s. This advanced form of skin cancer removal involves several stages of excision combined with microscopic assessment of the surgical margins during the surgery visit. It has an excellent success rate with low rates of cancer recurrence after treatment. In addition, the process of removal in stages minimizes the amount of adjacent healthy tissue that must be removed, reducing the size of the scar.

Mohs surgery is typically used to treat squamous cell carcinomas (SCCs) and basal cell carcinomas (BCCs) of the skin. It is sometimes also used to treat more rare types of skin cancer that require surgical removal to obtain clear margins.

  • BCC: The most common type of skin cancer. These are caused my UV damage to the skin from sun exposure and occur in areas of the body previously exposed to the sun. They often look like a skin-colored or red bump. Sometimes they bleed easily when traumatized.
  • SCC: The second most common type of skin cancer. These are also caused by sun damage and typically occur in areas of the body chronically exposed to the sun. They can look like a scaly patch, a red scaly bump, or a sore that won’t heal.
  • Melanoma: This is a less common but more aggressive type of skin cancer. Melanoma can develop anywhere on the body, within a pre-existing mole or as a new unusual looking brown spot. They can occur in sun-exposed or sun-protected areas. Mohs surgery is less commonly used to treat melanoma.

Mohs surgery can be performed anywhere on the body, including around the ears, eyes, lips and nose, on the fingers and toes, or on the genitals. It has a high cure rate, with a near 99% success rate in both previously untreated cancers.

Why Mohs Surgery is Performed in Stages

Mohs surgery involves microscopic assessment of margins during your surgery visit to ensure the cancer is cleared before the wound is sutured. The initial visible lesion or biopsy site is removed with a small margin, and the wound is then bandaged and the patient waits while the removed tissue is processed to make microscope slides. The Mohs surgeon then reviews the slides to check for any remaining cancer cells at the tissue margin. This process is repeated until clear surgical margins are obtained. By removing the cancer in stages, this allows the surgical margins to be narrower while still obtaining microscopically clear margins. This also allows confirmation that the cancer is gone before any stitches are placed.

This technique is very helpful at cancer clearance as squamous and basal cell carcinomas don’t always have visibly defined edges. Instead, it can help to think of their growth pattern like a tree, with root system extending deeper into the skin in varying directions, at various depths. Any cancerous cells left behind may continue to multiply, allowing the cancer to return. Mohs surgery ensures that no roots are left that can lead to cancer recurrence.

Mohs Surgery Stages Explained

The Mohs procedure consists of several stages, which allows for the removal of cancer, while minimizing the removal of healthy tissue. The step-by-step process takes place as follows:

  • The area to be treated is cleaned, marked and anesthetized. In the first stage, all visible cancer plus a narrow, additional margin is removed in a process that takes just a few minutes.
  • While you wait, the tissue removed is cut into sections, marked with ink, and a corresponding map of the tissue is drawn by the Mohs surgeon.
  • The cut sample is then frozen and sliced very thin. The tissue is then placed on microscope slides and stained with special dyes to make the cells more visible. These thin slices are examined under a microscope for signs of cancerous cells. This time-consuming process can take an hour or longer.
  • Your surgeon will carefully examine the edges and undersides of the removed tissue. If any cancer is remaining, the map is marked where cancer is still present and will guide round two of removal.
  • The process repeats as many times as necessary, until no cancerous cells are remaining.

Once the margins are clear of cancer, the Mohs surgeon will suture the wound if necessary to reduce scarring. Most wounds are fully healed within 4-6 weeks, but the exact time may vary depending on wound size.

How Many Stages Are Necessary for Full Removal?

It’s very difficult to predict ahead of time how many stages will be needed before the cancer is fully removed. Sometimes, a surgeon can make an educated guess by reviewing the pathology report of your first biopsy. Some types of skin cancer typically grow deeper and wider than others. Tumors of longstanding duration may also be larger and require more stages. However, every case is unique.

Your surgeon may be better able to estimate the number of stages needed once your procedure begins and the first stage is complete. That said, sometimes skin cancers have more extensive roots than are visible and can require multiple stages to clear.

While full removal is possible in a single stage, many people have their cancer successfully removed in two stages. In some cases, it takes three, four or more stages are required to achieve clear surgical margins.

Jessica “Nikki” Dietert, MD

Jessica “Nikki” Dietert, MD is a board-certified dermatologist ad fellowship-trained Mohs surgeon at Westlake Dermatology. She then earned her medical degree at The University of Texas Southwestern Medical School in Dallas before completing a residency at The University of Texas at Houston/M.D. Anderson Cancer Center, where she served as chief resident in her final year. She then finished training with a fellowship in Mohs micrographic surgery at Washington University in St. Louis.

One Response to “Mohs Surgery: How Many Stages Will Be Required?”

  1. Avatar Alice says:

    Good to know that there are no certain number of repetitions when it comes to Mohs surgery. Sounds like I should have my care giver be there for the whole day. Thanks for this

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