Mohs Surgery 101- Do I Need It and What to Expect

Mohs Surgery 101- Do I Need It and What to Expect

9 minute read

What is Mohs surgery?

Mohs surgery is a technique to help remove skin cancer. The Mohs technique offers two distinct advantages over conventional skin cancer surgery types:

1) It has the highest chances of fully removing the cancer, stifling regrowth

2) It allows the least amount of tissue to be removed from sites where preserving tissue is important such as the head, neck, hands, feet, groin, and the shin. Feel free to watch this educational video.  

Why is it called 'Mohs'?

Dr. Frederick Mohs, for whom the procedure is named, began developing this technique in the late 1930’s as a medical student. Now stay with us, we are about to get a bit technical.

He worked to evolve the procedure into a frozen section, margin controlled procedure where the physician acts both as the surgeon and as the pathologist. The technique has evolved such that the tissue is removed from the patient, where it is then mapped, inked, and processed in a disc type form. This allows for the tissue to be immediately frozen, cut, and stained with close to 100% of the margins being evaluated in a single plane. 

This differs from conventional processing of tissue where the tissue is prepared similar to removing slices from a loaf of bread and sent for formalin fixed paraffin embedding. The percentage of margin evaluated by the regular technique is estimated to only represent 2% of the actual tissue. 

Mohs surgery helps to minimize scarring and disfigurement from skin cancer surgery with the highest cure rate. The guidelines published in the Journal of the American Academy of Dermatology are available to the public as well as accessible through an app

Should I get Mohs surgery?

The decision whether to have Mohs, conventional surgery, curettage / electrodesiccation, topical chemotherapy, cryotherapy, oral / iv therapy, or radiation is dependent on multiple factors. This includes, but is not exclusive to, the type of tumor (basal cell carcinoma, squamous cell carcinoma, melanoma, merkel cell carcinoma, sarcoma), the size of the tumor, any vital or functional structures, and the overall well being of the patient. All of these factors and more are considered when making a decision as to whether or not Mohs surgery, even if indicated, is the best choice for the patient.  

It is important to be aware that the length of the scar often is around 3 times as long as it is wide (39 mm= 1/12 inch) in order for the skin tissue to move properly, under least tension to have a flat, smooth scar. However, there is no guarantee that your scar will be smaller, but you are less likely to need a second surgery due to either positive margins or recurrence in the appropriate clinical scenario with this procedure when appropriate. 

What to expect during your Mohs appointment

You will be brought to an examination room. Your temperature and vital signs will be taken and your medication, allergy, and any other medical alerts will be reviewed. Make sure to share any recent changes or updates to your information with your caregivers, including your pharmacy, emergency contact, and name of your primary care provider. You will be asked to sign a consent form indicating that you understand the risks and benefits of the procedure and wish to proceed. If you have taken any anti-anxiety medication, your provider will likely have asked you to have a witness and sign the consent prior to taking the medication. You must have a driver if you have taken anti-anxiety medication. 

You will likely be given a mirror or shown a photo taken of the site where the cancer was biopsied to verify that you agree that the location of the mark is where the procedure should take place. With easy access to digital photos, this usually is not an issue. However, if it will be more than a week or two before your procedure, make certain you can identify your biopsy site. You may want to mark the area with a sharpie or similar marker weekly and/or take a photo on your phone for good measure. 

Once the site has been verified and photographed, your site will be prepped with an appropriate antiseptic, numbed as it was for the biopsy. However, usually a larger volume of numbing is injected to allow for the site to remain numb before another procedure is being done. Some offices may add additional longer lasting anesthetic at this time. Because there is a larger amount of liquid injected, if the location is above your eyes or the front of your scalp, you may experience swelling and even black eyes for a few days after the procedure. As long as the wound is not tender, the swelling should slowly subside and be considered part of the procedure. If you are ever not sure, please contact your provider’s office. 

The Mohs surgeon will then remove the tissue to obtain the first stage specimen of your procedure. This typically does not take very long. The site is then bandaged, and the tissue is taken to the lab for processing. The length of time between processing and your surgeon reading your slide is highly unpredictable. There may be complex or large cases already in the lab or several cases ahead of yours. Feel free to ask for updates along the way, but typically 30-45 minutes is ideal. But don’t worry if it takes much longer, it is truly dependent on the other cases; trust that rushing will not give a better result. Try to plan for absolutely no other obligations the rest of the day other than to have your procedure and go home.   

Once the Mohs surgeon has reviewed your slides, they will determine if any tumor or cancer is left requiring further stages. The Mohs map from which the surgeon indicates residual cells is colored coded to be able to limit any further removals to the areas showing tumor + typically 2 mm overlap if indicated. The amount removed will be determined based on several pieces of information (tumor type, location, how it presents on the slide, characteristics of the patient’s overall health, history of prior treatments and risk of recurrence). If you have to have another stage, the process repeats. If you do not have another stage, then your surgeon and their team will talk with you about next steps. Sometimes the wound can heal on its own, known as secondary intention healing. You can also get suturing with a straight line, flaps, graft, or even skin substitutes. Your surgeon and their team will help with this decision. Make sure you understand your wound care instructions, pain management options (ice, acetaminophen, etc), and have a number to call if you have any concerns. 

If you or someone you know are having Mohs surgery, you will want to review the pre operative instructions to make certain you understand how to prepare for prior to your surgery, the day of, and post surgery. We know this can be a very anxiety provoking procedure. Surgery is never any fun, but when it's on your face, it takes it up a notch for sure. Having it on your hand is highly inconvenient and on your shin is no cake walk either (ask if you will need a cane or crutches). However, with proper preparation, you are likely to do very well. There is an article describing one woman’s journey with pictures and details of her experience that may be worthwhile for pre-surgery reading. 

I have linked my pre operative instruction page, but you should check with your surgeon as to exactly how he/she wants you to prepare for your day. The most challenging information to explain to our first time Mohs patients is how our patients are scheduled. It is not like having an arthroscopic procedure where the surgeon does one case, then moves on to the next. When a Mohs surgeon has a scheduled day for procedures, there can be 5-15 patients scheduled across a given time. Therefore, if there is a complex or large case ahead of you, you are at the mercy of the lab processing that specimen and the surgeon being able to also move on to the next patient who is ready for their next step whether it be a next stage, bandaging, or suturing. Good communication is helpful along the way, but honestly it is best to bring a book, a laptop, or whatever you need to keep you occupied while you wait. With COVID, we discourage having someone sit with you, but it is best if you can have someone drive you to and from your appointments. Check with your provider’s office to see what they recommend for your case. We typically suggest if the site is near the eyes, is extensive, or has an increased risk of bleeding (blood thinners), to have a driver. Each office has its own policy in this regard. 

Important Tips

  • If you start having some bleeding at home: hold pressure VERY FIRMLY for at least 10-15 minutes without checking, looking, dabbing, or peeking. If you look, it won’t clot. You must hold firm pressure directly over the wound in order to compress the blood vessels so they will clot.  
  • If your site is bleeding profusely, especially if you are on a blood thinner or you are not able to apply the pressure or have someone to help you do this, you may need to call 911 or have someone take you to the Emergency Room. 
  • Always wash your hands thoroughly before changing your bandages. Avoid touching the wound with your fingers. Use cotton balls, gauze, or q tips/cotton swabs as much as possible.  If your wound is hurting more rather than less each day, let your provider know as this may be important for them to know to help you avoid problems with healing.

Photo by Diana Polekhina on Unsplash

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