In last month’s issue, we provided a background to the types of skin cancer and drew attention to the astounding numbers of cases. In this month’s issue we will focus on the treatment of the common types of skin cancer with special focus on Mohs micrographic surgery. Typically, if someone has a suspicious growth – for example, an area on the face that bleeds easily and never heals, they will go to their doctor to have it examined. Some primary care doctors will perform a biopsy in the office themselves; while others will recognize that this growth may be a skin cancer and refer them to a dermatologist. The dermatologist will then perform a biopsy of the growth to determine if it is malignant (cancerous) or benign (non-cancerous). The purpose of the biopsy is not to remove the growth entirely, but to sample it to ascertain its characteristics. The biopsy is sent to another doctor, the pathologist, who will look at the skin under a microscope and generate a report back to the dermatologist. If the growth is confirmed to be a skin cancer, the dermatologist will either treat the cancer themselves or refer the patient to a skin cancer specialist and, in many cases, a Mohs surgeon.
DIFFERENT CANCERS NEED DIFFERENT TREATMENT
To refresh, there are three main types of skin cancer: basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and melanoma. BCC and SCC together account for 95% of all cases of skin cancer. Despite the fact that melanoma makes up less than 5% of skin cancer, it is responsible for about 80% of the deaths due to skin cancer, which is why we hear so much more about it in the news and society. Because melanoma can be deadly, the treatment options involve more aggressive surgery than for BCC or SCC, requiring removal of a large safety margin of normal skin to ensure that the melanoma is completely removed.
Treatment of BCC and SCC differs than treatment for melanoma. Because these cancers have a much lower chance of metastasizing (spreading to other parts of the body), the surgical margin for these cancers does not need to be as big. As long as the cancer is fully removed, there is no advantage to removing the large safety margin of normal skin like what is done for melanoma. Furthermore, because these cancers originate in outermost layer of the skin, the epidermis, a variety of treatment approaches exist depending on the characteristics of each individual cancer and patient. The enormous advantage to treating skin cancer as opposed to internal cancers is that dermatologists can see and feel these growths and assess their response to treatment.
MULTIPLE TREATMENT OPTIONS EXIST
The biggest risk factor for the development of skin cancer is chronic sun exposure and fair-skinned individuals who tend to burn easily are at highest risk. For this reason, skin cancer tends to develop in the areas of the body that accumulate the most damage from the sun’s rays – the scalp, face, neck, backs of the hands, shoulders, and shins. The approach to treatment will depend on the type of cancer, where it is located, whether or not it has been treated before, as well as individual patient factors. For instance, when tumors are very superficial and in areas that are less cosmetically sensitive such as the back, a procedure called electrodesiccation and curettage (ED&C) can be used. Colloquially referred to as a ‘scrape and burn’ procedure, the dermatologist numbs the skin and destroys the cancer by removing the top layer of skin. This only works for low-risk, thin cancers and does not work well on the head and neck. Other options such as freezing, topical creams, lasers or other light-based methods only work for very small, superficial cancers and do not yield a high enough cure rate for cancers that have had the chance to grow thicker or bigger, and should not be used for cancers on the face.
SURGERY IS THE GOLD STANDARD
With all of the above treatment approaches, the goal is to destroy the skin cancer. For small, thin cancers this results in cure rates around 90%. However, the main drawback with these treatment modalities is that the skin is destroyed, so there is nothing to analyze or look at under the microscope and hence, no way to confirm that the cancer has been removed. The only way to get feedback if a cancer has been treated adequately is with surgery because with surgery, skin that is removed can be looked at by a physician and determine if it is free of cancer. One can imagine that surgery on the back or the arm is a bit more straightforward than surgery on the nose or the lip. On the back, the dermatologist can numb the skin and remove the cancer with a small margin of normal skin (typically about ¼ inch on each side) and sew the remaining skin together in a straight line. This specimen then gets sent to a pathology center and the pathologist will examine the skin to determine if the cancer is completely removed. The advantages to this approach are that it is fairly quick and results in a high cure rate with minimal difficulties to the patient. The disadvantages are that BCC and SCC often have ‘roots’ or projections of the tumor that extend beyond the obvious cancer. So, on occasion, a report will return several days later that indicates the cancer has not been removed entirely and the procedure will need to be repeated.
MOHS MICROGRAPHIC SURGERY
Because about 85% of BCC and SCC occur on the head and neck, it is often not possible to remove a cancer with a wide enough margin of normal skin without encroaching upon important areas such as the lips, ears, or eyelids. Furthermore, once a cancer has been removed from an area such as the nose or the eyelid, it is often not possible to sew the edges of the skin directly together and complicated surgical reconstruction of the skin is needed. It would not be advisable for a physician to perform an intricate reconstructive procedure without first confirming a cancer has been removed. In these cases when skin cancers are in high-risk areas, when tumors are aggressive or infiltrative in their growth patterns, or when their edges are ill-defined, Mohs micrographic surgery results in the highest cure rates and is the treatment of choice.
What is Mohs micrographic surgery?
Mohs micrographic surgery, or simply Mohs surgery, is named in honor of Dr. Frederic Mohs, the physician who developed the technique over 50 years ago. Since then, many technical improvements and refinements have established it as the most definitive way for treating BCCs and SCCs. The major difference between Mohs surgery and the methods listed above is meticulous microscopic control. With Mohs surgery, the pathology laboratory is in the surgical office and the surgeon also acts as the pathologist. With the advantages of having a laboratory on-hand and undergoing training in how to look at skin under the microscope, the Mohs surgeon can remove the skin cancer layer by layer and examine the removed tissue under the microscope until normal (cancer-free) skin is obtained while the patient waits in the office. By evaluating 100% of the edges of the removed skin, the highest rates of tumor clearance are obtained and the chances of the cancer growing back are close to zero. In fact, by using the Mohs technique, cure rates for treating skin cancer approach 99%.
The other main advantage of having microscopic control with Mohs surgery is that the amount of healthy tissue removed is kept to minimum. While other methods have to roughly estimate the amount of normal tissue to remove, often unnecessarily large amounts of normal skin can be removed, or recurrence of the tumor can happen if any cancer is left behind. With Mohs surgery, the cancer is removed while removing the least amount of healthy skin. This maximizes the functional and cosmetic outcome resulting from surgery. Once the Mohs surgeon has confirmed that the skin cancer has been removed, then reconstruction of the area occurs on the same day in the same office. In addition to training in skin cancer surgery and pathology, Mohs surgeons also undergo training in facial reconstruction. By removing the cancer and the smallest amount of normal skin, areas of the face can be repaired with the least cosmetic impact and the best results.
For more information:
The American College of Mohs Surgery:
Sherrif Ibrahim, MD PhD is Assistant Professor of the URMC Department of Dermatology and the Wilmot Cancer Center. His practice is focused on procedural and surgical dermatology including the management of skin cancer with Mohs surgery.