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Mohs Microscopically Controlled Excision

Last updated June 2, 2021

Written by: Lester Fahrner, MD

Reviewed by: Lester Fahrner, MD

Approved by: Krish Tangella MD, MBA, FCAP

Mohs Microscopically Controlled Excision (for difficult skin cancers) is a procedure used in cases where the distinction between skin cancer cells and normal tissue is difficult, with the usual Mohs rapid technique of frozen sections and routine histology stains.


Background Information:

What are the other Names for the Procedure?

  • Geometric Staged Excision with Margin Control
  • Slow Mohs Staged Excision

What is Mohs Microscopically Controlled Excision surgical procedure?

  • Mohs Microscopically Controlled Excision (for difficult skin cancers) is a procedure used in cases where the distinction between skin cancer cells and normal tissue is difficult, with the usual Mohs rapid technique of frozen sections and routine histology stains
    • Fixed tissue is used, and immunohistochemical stains are used to highlight the malignant cells within the tissue specimens
    • The excision stages are done most frequently without the beveled, 45-degree angle of the cut for normal Mohs
    • A 90-degree traditional vertical cut is made, and the tissue passed to a dermatopathologist
  • The Mohs surgeon creates the Mohs map, which is shared with and referred to collaboratively by both physicians
  • The immunohistochemical stains and their interpretation may take about a day, so the surgical defect is made free of bleeding, and bandaged as appropriate for a day’s wait
  • Any residual tumor is noted in consultation between the surgeon and pathologist, and another stage of the Slow Mohs surgery done
  • This process is repeated until the skin cancer is completely removed. The surgical defect is evaluated, and a reconstruction plan made

Mohs Microscopically Controlled Excision is generally performed on skin cancers which require more complex pathology examination than routine Mohs micrographic surgery. The skin cancer types most often treated with this technique include:

  • Melanoma
  • Melanoma in situ (confined to the epidermis, not invasive)
  • Dermatofibrosarcoma protuberans (DFSP)
  • Extramammary Paget’s disease (EMPD)
  • Sebaceous carcinoma
  • Microcystic adnexal carcinoma (MAC)
  • Atypical fibroxanthoma (AFX)
  • Merkel cell carcinoma
  • Squamous cell carcinoma (SCC), high-risk subtypes
  • Basal cell carcinoma (BCC), high-risk subtypes

What part of the Body does the Procedure involve?

The Mohs Microscopically Controlled Excision procedure involves the following:

  • High risk tumors of the face, scalp, neck, hands, feet, or genital area
  • Any location on the body is potentially addressed, particularly with high risk malignancies

Why is the Mohs Microscopically Controlled Excision surgical procedure Performed?

Mohs Microscopically Controlled Excision is primarily performed for skin cancers in which it is difficult to determine cells that are malignant from normal tissues and cells.

What are some Alternative Choices for the Procedure?

Some of the alternative choices for Mohs Microscopically Controlled Excision include:

  • Traditional elliptical excision, with repeat surgery required if margins are positive for cancer cells
  • Mohs micrographic surgery - traditional frozen sections with an additional stage taken for immunohistochemical studies

What are the Recent Advances in the Procedure?

Some of the recent advances include rapid immunohistochemical test which can shorten the evaluation time, making more than one surgical stage per day possible. This can speed up the cancer removal process, which is beneficial for patient well-being.

What is the Cost of performing the Mohs Microscopically Controlled Excision surgical procedure?

The cost of the Mohs Microscopically Controlled Excision procedure depends on a variety of factors, such as the type of your health insurance, annual deductibles, co-pay requirements, out-of-network and in-network of your healthcare providers and healthcare facilities.

In many cases, an estimate may be provided before the procedure. The final amount depends upon the findings during the surgery/procedure and post-operative care that is necessary.

When do you need a Second Opinion, prior to the Procedure?

  • It is normal for a patient to feel uncomfortable and confused with a sudden inflow of information regarding the Mohs Microscopically Controlled Excision procedure and what needs to be done
  • If the patient needs further reassurance or a second opinion, a physician will almost always assist in recommending another physician
  • Also, if the procedure involves multiple steps or has many alternatives, the patient may take a second opinion to understand and choose the best one. They can also choose to approach another physician independently

What are some Helpful Resources?

https://www.aad.org/ (accessed on 05/16/2021)

https://www.mohscollege.org/ (accessed on 05/16/2021)

https://www.mohssurgery.org/ (accessed on 05/16/2021)

Prior to Mohs Microscopically Controlled Excision surgical procedure:

How is the Mohs Microscopically Controlled Excision surgical procedure Performed?

The Mohs Microscopically Controlled Excision procedure is performed in the following manner:

  • The Mohs surgeon determines the perceived clinical extent of the known skin malignancy
  • Based on the biology of the type of skin cancer and their clinical experience, a sterile marking pen is used to indicate the excision lines
  • The surgical specimens are excised, usually as straight thin strips of tissue
  • These specimens are marked with sutures or tissue dyes to orient them with respect to the corresponding anatomic position on the patient
  • A Mohs map is drawn by the surgeon as a permanent record, to use in following the progression of the procedure
  • The tissue specimens and a copy of the Mohs map are passed on to the pathologist
  • Typically, the pathologist holds consultation with the surgeon, to be informed of the tumor type, its anticipated biologic behavior, and the immunohistochemical stains they will use
  • The bulk of the skin cancer is then removed (portion inside the just-sampled margin specimens)
  • Sutures and electrocautery are used to control bleeding caused by the excisions
  • A dressing is applied which will keep the surgical wound dry and protected until the return visit (usually the next day)

Where is the Procedure Performed?

The procedure is usually performed in a clinic surgical suite or outpatient surgical suite specifically equipped, staffed, and stocked to perform the Mohs micrographic surgery and Mohs Microscopically Controlled Excision.

Who Performs the Procedure?

The Mohs Microscopically Controlled Excision procedure is usually performed by a physician trained in Mohs surgery.

  • Physicians trained as dermatologists most commonly perform the procedure
  • However, physicians trained in plastic surgery, head and neck (ENT) surgery, as well as oral and maxillofacial surgery can also perform the procedure

For Mohs Microscopically Controlled Excision, a pathologist is a necessary key team member, to prepare, interpret, and consult on the cancer under treatment.

How long will the Procedure take?

The Mohs Microscopically Controlled Excision procedure usually takes at least a day. The first stage of the procedure may take under an hour. The remainder of the time, the patient is free to go until the next day, when the results of the pathology exam will be known. However, the overall procedure can extend over several days.

What do you need to tell your Physician before the Procedure?

It is very important to provide the following information to your healthcare provider. This enables your healthcare provider in assessing the risks for the procedure and helps avoid complications.

  • Provide medical history such as diabetes, hypertension, heart disease, etc. (if any)
  • Provide a complete list of medications you are currently taking to your physician. This information is useful for a variety of reasons. For example, it can help your healthcare provider prevent complications due to a drug interaction
  • If you are allergic to any specific medication or food items
  • If you are taking blood thinners, such as aspirin, warfarin, herbal supplements, or any other such medications
  • Any medical or family history of bleeding disorders or blood clots
  • If you have ever been diagnosed with blood clots in your leg (deep vein thrombosis) or lung (embolism of lung)
  • Any unusual effects of anesthesia from prior surgery
  • If you have a history of frequent bone fractures (this may affect bone-healing, if bones are involved as part of your procedure)
  • A list of all previous surgical procedures you have undergone, like for example - removal of appendix, gallbladder, or any other part, of your body; surgical repair of any body part, such as hernia repair, perforation of bowel wall, etc.
  • Information about any implanted electronic medical devices such as pacemakers, defibrillators, pain control devices, or deep brain stimulators for Parkinson’s disease or seizures
  • Any joint implants, and if the surgeon who implanted them recommends preoperative antibiotics

What Preparations are needed, prior to the Procedure?

The physician performing the procedure will evaluate the patient prior to the procedure and discuss the details with risks for complications and obtain his/her permission (termed informed consent).

  • Some medications increase a person’s chances of bleeding and it may be recommended to discontinue them for a period of time, before the procedure is performed
  • Blood tests may be performed to determine if there is a bleeding tendency or any other medical conditions that prevents the person from undergoing the procedure
  • Blood work, glucose, and pregnancy tests (if applicable) will be undertaken per physician recommendations
  • If anesthesia team is involved in the procedure, then they too will discuss details of anesthesia with risks for complications and obtain permission from the patient (informed consent)
  • Avoid application of any deodorant or topical medicines on the area, prior to the procedure
  • It is advisable to quit smoking and the use of any nicotine based products, for a while, before the procedure
  • Consumption of alcoholic drinks must also be avoided for a period of time, as instructed
  • Generally, the patient is told to eat, as they are awake for the procedure
  • Individuals with diabetes, hypertension, or other cardiac conditions, are required to discuss these (including medications being taken) with their attending physician well in advance
  • For individuals with diabetes, it is important that the blood sugar stays within the normal range; if not, their diabetologist may have to control blood sugar by recommending insulin and/or a combination of oral medicines

Pregnant women and individuals with severe underlying sicknesses are advised to inform the surgeon or staff of their health status.

What is the Consent Process before the Procedure?

The physician will obtain permission for the Mohs Microscopically Controlled Excision procedure using an Informed Consent Form.

Consent for the Procedure: A “consent” is the approval to undergo a procedure. A consent form is signed after the risks and benefits of the procedure, and alternative treatment options, are discussed. This process is called informed consent.

In case of minors and individuals unable to give informed consent, the parent or legal guardian or next of kin can sign the consent for the procedure.

What Tests are needed, before the Mohs Microscopically Controlled Excision surgical procedure?

In many cases, no tests are typically necessary prior to the Mohs Microscopically Controlled Excision procedure. However, if required, the healthcare provider may recommend the following tests such as:

  • Blood tests, which identify the status of the clotting system
  • Imaging studies if they might help determine the extent of the tumor (cancer)

What are some Questions for your Physician?

Some of the questions that you might ask your healthcare provider are as follows:

  • What is a Mohs Microscopically Controlled Excision procedure?
  • Why is this procedure necessary? How will it help?
  • How soon should I get it done? Is it an emergency?
  • Who are the medical personnel involved in this procedure?
  • Where is the procedure performed? 
  • What are the risks while performing the procedure?
  • What are the complications that might take place during recovery?
  • How long will it take to recover? When can I resume normal work?
  • How many such procedures have you (the physician) performed?
  • Are there any follow-up tests, periodic visits to the healthcare facility required, after the procedure?
  • What are the costs involved?

During the Mohs Microscopically Controlled Excision surgical procedure:

What kind of Anesthesia is given, during the Procedure?

In most cases, local anesthetic is injected for the Mohs Microscopically Controlled Excision procedure. Some patients request a short-acting benzodiazepine pill to decrease anxiety. 

Note: These patients will need a driver to take them home.

How much Blood will you lose, during the Procedure?

There may be some blood loss involved as part of the Mohs Microscopically Controlled Excision procedure.

What are the possible Risks and Complications during the Mohs Microscopically Controlled Excision surgical procedure?

There are general factors that increase one’s risk of getting complications during the Mohs Microscopically Controlled Excision procedure, which include:

  • Obesity: Generally greater the degree of obesity, greater is the surgical risk
  • Smoking: Longer the smoking history (in pack years smoked), greater the surgical risk
  • Advancing age
  • Poorly controlled diabetes, as evidenced by a high hemoglobin A1c and a high fasting glucose
  • Poorly functioning kidney, as evidenced by increased BUN (blood urea nitrogen) and blood creatinine
  • Poorly functioning liver, as evidenced by increased blood liver function tests
  • Hypertension (increased blood pressure), especially if it is poorly controlled
  • Poor nutritional status (malnutrition with mineral and vitamin deficiencies)
  • Poor lung function, as evidenced by abnormal lung function tests
  • History of bleeding disorders
  • Poor immune system due to a variety of causes

Some of the possible risks and complications that may arise during a Mohs Microscopically Controlled Excision procedure include:

  • Infection
  • Bleeding
  • Injury to the neighboring structures
  • Pain
  • Discomfort
  • Anesthetic complications
  • Need for further procedures
  • Pneumonia
  • Blood clot formation, affecting blood supply to the buttocks and lower extremities
  • Heart problems

Please note that the complication and risks that may arise during the surgery is governed by factors such as prior significant health problems.

What Post-Operative Care is needed at the Healthcare Facility after the Mohs Microscopically Controlled Excision surgical procedure?

At the healthcare facility, generally there is no requirement for any post-procedure care, unless any complications arise. However, immediately following the surgery, the patient will be observed to make certain they are able to safely leave the facility. It is often advisable to have the patient abstain from driving for a day.

After the Mohs Microscopically Controlled Excision surgical procedure:

What are the possible Risks and Complications after the Mohs Microscopically Controlled Excision surgical procedure?

The risks and complications that may arise after Mohs Microscopically Controlled Excision include:

  • Excessive bleeding that may sometimes require an additional surgical procedure
  • Any symptom that causes uneasiness such as nausea and dehydration
  • Low-grade fever
  • Infection of the surgical wound

What is the Prognosis after the Surgery?

The prognosis depends on a set of several factors that include:

  • The extent of the Mohs Microscopically Controlled Excision procedure
  • The size and complexity of the reconstructive procedure to correct the surgical defect
  • The underlying biology of the skin cancer that required treatment
  • The ability of the procedure to completely clear the margins
  • The possible need for postoperative chemotherapy, biologically targeted therapy, or radiation therapy
  • The underlying generally health of the patient

When do you need to call your Physician?

Do contact your physician or call 911 (or your local emergency number) based on the seriousness of any of the following symptoms:

  • Fever and chills
  • Severe pain
  • Shortness of breath
  • Bleeding or fluid discharge from the surgical wound
  • Nausea and vomiting
  • Signs of infection
  • Severe fatigue
  • Dizziness

What Post-Operative Care is needed at Home after the Mohs Microscopically Controlled Excision surgical procedure?

At home, the following post-operative care is recommended after a Mohs Microscopically Controlled Excision procedure:

  • Use a cold pack over the dressing to decrease swelling and bleeding risk. Follow the written guidelines on this, and all other post-operative care instructions provided
  • Resume showering, but keep the dressing dry and protected 
  • Replace dressing after showering if instructed
  • Take the prescribed medications following the procedure
  • Avoid any strenuous activity for a period recommended by the physician
  • Do not drive (post-procedure) for a period of 24 hours
  • Avoid smoking or drinking alcohol post-procedure
  • Continue old prescribed medications after checking with the healthcare provider
  • Contact the concerned healthcare provider if there are any questions regarding one’s care

How long does it normally take to fully recover, from the Procedure?

The recovery time usually depends on the extensiveness of the surgery. Simple procedures have shorter recovery periods. Less extensive reconstructive procedures to repair the defect also heal more quickly. All patients should anticipate at least 4 weeks until healing starts towards completion.

Additional Information:

What happens to tissue/samples (if any), taken during the Procedure?

The tissue is taken for further examination and later disposed, as per the standard medical procedure.

When should you expect results from the pathologist regarding tissue taken out, during the Procedure?

  • The samples/tissue is processed in the laboratory under a pathologist's supervision
  • Slide(s) are prepared once the tissue is processed and this is examined by a pathologist and a pathology report issued
  • Depending on the complexity of the case, issue of the report may take anywhere between 4-24 hours

Who will you receive a Bill from, after the Mohs Microscopically Controlled Excision surgical procedure?

It is important to note that the number of bills that the patient may receive depends on the arrangement the healthcare facility has with the physician and other healthcare providers.

Sometimes, the patient may get a single bill that includes the healthcare facility and the consultant physician charges. Sometimes, the patient might get multiple bills depending on the healthcare provider involved. For instance, the patient may get a bill from:

  • The outpatient facility or hospital
  • The dermatologist
  • A pathologist 
  • The laboratory at which the specimens are processed

The patient is advised to inquire and confirm the type of billing before the Mohs Microscopically Controlled Excision procedure is performed.

Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: June 2, 2021
Last updated: June 2, 2021