What is Mohs Surgery

Mohs surgery is the most effective and advanced treatment for skin cancer today. It offers the highest potential for cure – even if the skin cancer has been previously treated by another method.

Originally developed in the 1930s, Mohs micrographic surgery has been refined into the most advanced, precise, and effective treatment for an increasing variety of skin cancer types. With the Mohs technique, Dr. Swengel can precisely identify and remove an entire tumor while leaving the surrounding healthy tissue intact and unharmed

Mohs Surgery successfully removes high risk skin cancers with tissue sparing techniques unique to Mohs surgery. This enables optimal removal, lowest risk of recurrence and minimal scarring.
The Mohs procedure involves surgically removing skin cancer layer by layer and examining the tissue under a microscope until healthy, cancer-free tissue around the tumor is reached (called clear margins).

Because Dr. Steven Swengel is specially trained as a cancer surgeon, pathologist, and reconstructive surgeon, Mohs surgery has the highest success rate of all treatments for skin cancer – up to 99%

Mohs surgery offers the highest cure rate among treatments for skin cancer and can be used for practically any type of skin cancer.

There are many other acceptable skin cancer treatment options including freezing (cryosurgery), scraping & burning, surgical removal (excision), and laser surgery, which all require the surgeon to estimate how extensively to treat the area around the tumor.

There are many advantages to Mohs surgery compared to other other skin cancer treatments including its high cure rate and cost-effectiveness. It is especially appropriate for skin cancers that:

  • Develop on areas where preserving cosmetic appearance and function are important
  • Have recurred after previous treatment or are likely to recur
  • Are located in scar tissue
  • Are large
  • Have edges that are ill-defined
  • Grow rapidly
Mohs surgery is unique and so effective because of the way the removed tissue is microscopically examined, evaluating 100% of the surgical margins. The pathologic interpretation of the tissue margins is done on site by your Mohs surgeon, Dr. Steven Swengel, who is specially trained in the reading of these slides and is best able to correlate any microscopic findings with the surgical site on the patient.

Advantages of Mohs surgery include:

  • Ensuring complete cancer removal during surgery, virtually eliminating the chance of the cancer growing back
  • Minimizing the amount of healthy tissue lost
  • Maximizing the functional and cosmetic outcome resulting from surgery
  • Repairing the site of the cancer the same day the cancer is removed, in most cases
  • Curing skin cancer when other methods have failed

Other skin cancer treatment methods blindly estimate the amount of tissue to treat, which can result in the unnecessary removal of healthy skin tissue and tumor re-growth if any cancer is missed.

The Mohs Step-by-Step Process

The Mohs surgery procedure seems simple: Dr. Swengel removes the cancer, carefully checks to be sure that he got it all, then repairs the wound.

American College of Mohs Surgery members like Dr. Swengel however, train in and practice the complex nuances of this process for years so they are prepared to handle any situation they may encounter.

The steps they follow for each Mohs surgical procedure are shown below.

Mohs Procedure Step 1 RefinedMDThe roots of a skin cancer may extend beyond the visible portion of the tumor. If these roots are not removed, the cancer will recur. A surgery starts with Dr. Swengel examining the visible lesion and planning what tissue to remove. The patient then receives local anesthesia, and the Mohs surgery begins.
Mohs Procedure Step 2 RefinedMDDr. Swengel removes the visible portion of the tumor using careful surgical techniques.



Mohs Procedure Step 3 RefinedMDDr. Swengel next removes a deeper layer of skin and divides it into sections. With the help of technicians, he then color-codes each of these sections with dyes and makes reference marks on the skin to show the source of the sections. A map of the surgical site is then drawn to track exactly where each small portion of tissue originated.


mohs-procedure-4In a laboratory, Dr. Swengel uses a microscope to examine the undersurface and edges of each section of tissue in search of evidence of remaining cancer.





mohs-procedure-5If Dr. Swengel finds cancer cells under the microscope, he will mark their location on the “map” and returns to the patient to remove another deeper layer of skin — but only from precisely where the cancer cells originated. This method ensures that the Mohs surgery results in the smallest scar possible.
The removal process stops when there is no longer any evidence of cancer in the surgical site. Because Mohs surgey removes only tissue containing cancer, it ensures that the maximum amount of healthy tissue is kept intact.

At this point, Dr. Swengel discusses reconstruction options, should they be required, and then post-operative care. Mohs surgery recovery tends to be easily manageable because of the use of local anesthesia and the careful surgical techniques.

Mohs Surgery Reconstruction Options



While treatment of your skin cancer is your primary concern, reconstruction of the treated area is also important. After your Mohs surgeon, Dr. Swengel, is confident that all of the cancer has been removed, together you will determine how the wound will be repaired. In addition to removing skin cancer, fellowship trained Mohs surgeon, Dr. Swengel, have specialized reconstructive surgery training for repairing the wound.

While Dr. Swengel might be able to give you an idea of whether your reconstruction should take place immediately after surgery or be delayed until later, it’s impossible to know the extent of the cancer in advance.

After determining that the affected area is cancer free and reconstruction is necessary, Dr. Swengel will review skin cancer reconstructive surgery options with you. Depending on the size of the tumor, depth of roots, and location, one of the following options will be selected:

  • Small, simple wounds may be allowed to heal by themselves (process known as secondary-intention healing)
  • Slightly larger wounds may be closed with stitches in a side-to-side fashion
  • Larger or more complicated wounds may require a skin graft from another area of the body or a flap, which closes the defect with skin adjacent to the wound
  • On rare occasions, the patient may be referred to another reconstructive surgical specialist.

Mohs Surgery Procedure Post Operative After Care

After a Mohs surgery procedure, most patients find the recovery process simple and easy thanks to the streamlined surgical approach that leaves surrounding tissue unharmed.

Nonetheless, it’s common for patients to wonder what they can expect after a Mohs skin cancer surgery. It’s also important to use the post-operative period to plan an ongoing skin cancer detection strategy for the future.

After a Mohs surgical procedure, you may or may not undergo a repair process to mend the wound left by the surgery. A number of different reconstruction options exist, and instructions for aftercare are different depending on which approach Dr. Swengel takes.

Dr. Swengel and his medical team will provide you with detailed instructions to follow at home, and it’s important you do so in order to enhance your healing and final outcome. These instructions will include:

  • Information about when to change bandages and how to clean the surgical site
  • Medication information about prescription or over-the-counter pills or topical ointments
  • A timeline for when you can return to certain activities, such as wearing makeup or exercising
  • A schedule of follow-up appointments to remove any stitches and monitor your healing
  • Recommendations for treating your Mohs surgery scar to ensure it heals and fades quickly

Because American College of Mohs Surgery (ACMS) members like Dr. Swengel perform the procedure in an outpatient setting using only local anesthesia, immediate recovery generally involves little more than resting and simple wound care.

Some patients may experience mild discomfort, bleeding, redness, or inflammation, but these are typically temporary and easily manageable.

Although Mohs micrographic surgery has an extremely high success rate that frequently prevents skin cancer from recurring at the same site, monitoring is still very important for Mohs patients.

Once you discover that you are prone to skin cancer, diligence is crucial for detecting any new lesions that may form elsewhere on your body.

Dr. Swengel and his medical team arrange a schedule of post-surgical checkups that may extend many years into the future. He or she also gives you specific strategies for recognizing skin cancer symptoms so you can develop good detection habits at home.

Your Mohs Surgeon, Dr. Steven Swengel.

Dr. SwengelDrSwengel-full has been doing Mohs Surgery and managing skin cancers in patients for over 32 years while at Kaiser Permanente in San Jose.

He brought fresh tissue Mohs surgery to northern California after his residency in dermatology at the University of Michigan where he did additional training in Mohs Surgery.

While practicing with Kaiser Permanente has was Chief of Dermatology and Mohs Surgery Unit. He has performed 15,000+ Mohs cases during his career and countless other skin cancers treated with other surgical approaches.

He is a fellow in the American College of Mohs Surgery since 1983 as well as a fellow in the American Academy of Dermatology, The American Society of Dermatology Surgery and the American College of Laser Medicine and Surgery

Mohs Surgery at Refined Dermatology

At the Mohs Surgery Unit of Refined Dermatology, we are committed to providing you with state of the art Mohs micrographic surgery.

If we know the defect from surgery will be large, functionally difficult, or require multiple stages of closure, we offer the upmost respect, care and professionalism.

About the Mohs Unit at Refined Dermatology

The Refined Dermatology Mohs Unit of Steven Swengel MD and Associates islocated at 800 Pollard Road, Bldg A in Los Gatos , CA. We are directly across from El Camino Los Gatos Hospital and most easily accessed via the Winchester Exit on Highway 85.

We comprise the surgical wing of the building where we have three spacious surgery rooms as well as private lounge areas both inside and out where you can rest between surgical sessions.

We respect your time during the day of Mohs surgery and avoid the day long events everyone has experienced in the past. Our goal is to get morning patients cleared and repaired by lunch time and afternoon patients home by dinnertime.

Rarely will anyone have to experience an all day event in our center. Doing it this way keeps everyone a little fresher and a lot happier.

The Mohs Unit is a CLIA certified laboratory under the direct supervision of Steven Swengel, MD who is a fellow in the American College of Mohs Surgery. All tissue is processed by two of the finest licensed histotechs who he hired and have worked with him for over 25 collective years.

We also have the tools and laser equipment available to provide dramatic improvement in scars whether they be after Mohs surgery or any other surgery or condition.

Once the Mohs surgery has given us tumor free margins, we take the time to step back, assess the wound and discuss with you the best options for optimal healing.

Most wounds can be easily closed the same day, but there may be the need for closure the next day or arranging an orchestrated repair with a facial plastic or plastic surgeon if we know the defect will be large, functionally difficult, or require multiple stages of closure.

Frequently Asked Questions

The term “Mohs” refers to Dr. Frederic Mohs, Professor of Surgery at the University of Wisconsin, who developed this surgical technique in the 1930s. The technique has undergone many refinements and has come to be known as “Mohs micrographic surgery” or simply “Mohs surgery” in honor of Dr. Mohs.
You want your skin cancer treatment to be performed with the highest standards of quality and competency. The American College of Mohs Surgery is the only organization that requires its members to have successfully completed an extensive fellowship that requires at least one full year of training and hands-on experience provided by highly qualified instructors after completing their years of residency training.
Dr. Mohs recognized that a skin cancer often resembles the “tip of the iceberg” with more tumor cells growing downward and outward into the skin like the roots of a tree. These “roots” are not visible with the naked eye, but can be seen under a microscope.

Mohs surgery is a highly specialized and precise treatment for skin cancer in which the cancer is removed in stages, one tissue layer at a time. It is an outpatient procedure, performed under local anesthesia, and is distinguished by a specific technique of tissue examination that is unique to Mohs surgery. Although other surgical specialists may check excision margins, this form of pathologic examination of the tissue is not the same as Mohs surgery.

Once a tissue layer is removed, its edges are marked with colored dyes, and a map of the specimen is created. The tissue is then processed onto microscope slides by a Mohs histotechnician. These slides are carefully examined under the microscope by the Mohs surgeon so that any microscopic roots of the cancer can be precisely identified and mapped.

If cancer cells are seen, an additional tissue layer is removed only in areas where the cancer is still present, leaving normal skin intact. This saves as much normal, healthy skin as possible.

Once the cancer has been removed, the Mohs surgeon will explain options for repair of the wound, including natural healing (granulation), stitching the wound together using a side-to-side closure, or using a skin flap or graft.

It’s important to choose a fellowship trained Mohs surgeon who is a member of the American College of Mohs Surgery. Mohs College surgeons have undergone at least 1 year of fellowship training beyond dermatology residency, which allows for additional experience in all of these specialized processes and techniques.

Yes. Following a biopsy, your skin cancer may no longer be visible. However, the surface lesion that was removed can represent the “tip of the iceberg.” More tumor cells may remain in the skin. These can continue to grow downward and outward, like roots of a tree. These “roots” are not visible with the naked eye. If they are not removed, the tumor will likely reappear and require more extensive surgery.

Tumors that are neglected can spread deeply into the skin and invade nearby structures. On rare occasions, these cancerous cells can metastasize to lymph nodes and other organs in the body.

Mohs surgery has the highest cure rate. It is appropriate for most skin cancers and especially suitable for skin cancer that:

  • Is in an area where it is important to preserve healthy tissue for maximum functional and cosmetic result
  • Was treated previously and has come back
  • Is located near scar tissue
  • Is large
  • Does not have clearly defined edges
  • Is growing rapidly or uncontrollably
  • Is of an aggressive subtype (i.e., sclerosing or infiltrating basal cell carcinoma)
  • Develops in organ transplant or lymphoma patients

Please note: the above list is not exhaustive of all of the instances where Mohs surgery is the most appropriate option for your skin cancer.

Although Mohs surgery can take longer than other techniques to perform, advances in technology, such as automated staining of tissue samples, have made it quicker. While it is impossible to predict exactly what timeframe to expect for each Mohs surgery procedure, the entire procedure usually lasts several hours. Rarely, clearing the tumor and reconstructing the defect can take the better part of a day. A consultation with Dr. Swengel prior to your procedure will allow him to understand the unique qualities of your situation and enable him to more clearly estimate the extent of the timeframe for the surgery.
Yes. As will any treatment for skin cancer, Mohs surgery will leave a scar.

Mohs surgery preserves as much healthy skin as possible and maximizes options for repairing the surgical defect, once the tumor is completely removed. Once Dr. Swengel has completely removed your skin cancer through Mohs surgery, reconstruction for optimizing the final functional and cosmetic result becomes the highest priority.

Generally, a post-surgical scar improves with time and can take up to 1 year or more to fully mature. As your surgical site heals, new blood vessels can appear and support the healing changes occurring underneath the skin. This can result in the reddish appearance of the scar. This change is temporary and will improve with time.

In addition, the normal healing process involves a period of skin contraction, which often peaks 4 to 6 weeks after the surgery. This may appear as a bumpiness or hardening of the scar. On the face, this change is nearly always temporary and the scar will soften and improve with time.

If you have a history of abnormal scarring, such as hypertrophic scars or keloids, or if there are problems with the healing of your scar, injections or other treatments may be used to optimize the cosmetic result. Dr. Swengel is available for you throughout the healing process to discuss any concerns that may arise.

When assessing the cost-effectiveness of Mohs surgery there are several factors to consider. Because of the number of personnel involved as well as the advanced technology required, the initial procedure is often more costly than other treatment methods. However, because of the procedure’s high success rate, most patients require only a single surgery. This surgery usually includes the repair of the wound as well. While other methods might initially be less expensive than Mohs surgery, additional surgeries and pathology readings are required to repair the wound and to treat the cancer if it is not completely removed. Each of these additional surgeries and pathology readings will require separate fees, while a single Mohs surgery procedure includes all of these into one fee.


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