Surgical Techniques Improve
The first step in treatment is the removal of the melanoma, and the standard method of doing this is by surgical excision (cutting it out). Surgery has made great advances in the past decade, and much less tissue is removed than was customary in the past. Patients do just as well after the lesser surgery, which is easier to tolerate and produces a smaller scar.
Surgical excision is also called resection, and the borders of the entire area excised are known as the margins.
In most cases, the surgery for thin melanomas can be done in the doctor’s office or as an outpatient procedure under local anesthesia. Stitches (sutures) remain in place for one to two weeks, and most patients are advised to avoid heavy exercise during this time. Scars are usually small and improve over time.
Discolorations and areas that are depressed or raised following the surgery can be concealed with cosmetics specially formulated to provide camouflage. If the melanoma is larger and requires more extensive surgery, a better cosmetic appearance can be obtained with flaps made from skin near the tumor, or with grafts of skin taken from another part of the body. For grafting, the skin is removed from areas that are normally or easily covered with clothing.
There is now a trend towards performing sentinel node biopsy and tumor removal surgery at the same time, provided the tumor is 1 mm or more thick. When the procedures are combined in this way, the patient is spared an extra visit.
Setting The Margins
In the new approach to surgery, much less of the normal skin around the tumor is removed and the margins, therefore, are much narrower than they ever were before. This spares significant amounts of tissue and reduces the need for postoperative cosmetic reconstructive surgery.
Most US surgeons today follow the guidelines recommended by the National Institutes of Health and the American Academy of Dermatology Task Force on Cutaneous Melanoma.
- When there is an in situ melanoma, the surgeon excises 0.5-1 centimeter of the normal skin surrounding the tumor and takes off the skin layers
down to the fat.
- In removing an invasive melanoma that is 1 mm or less in Breslow’s thickness, the margins of surrounding skin are extended to 1 cm and the excision goes through all skin layers and down to the fascia (the layer of tissue covering the muscles).
- If the melanoma is 1.01 to 2 mm thick, a margin of 1-2 cm is taken.
- If the melanoma is 2.01 mm thick or greater, a margin of 2 cm is taken.
These margins all fall within the range of what is called “narrow” excision. When you consider that until recently, margins of 3 to 5 cm (wide excision) were standard, even for comparatively thin tumors, you can see how dramatically surgery has changed for the better. Physicians now know that even when melanomas have reached a thickness of 4 mm or more, increasing the margins beyond 2 cm does not increase survival.
Mohs Micrographic Surgery
In recent years, Mohs Micrographic Surgery, which many physicians consider the most effective technique for removing basal cell and squamous cell carcinomas (the two most common skin cancers), is being increasingly used as an alternative to standard excision for certain melanomas. In this technique, one thin layer of tissue is removed at a time, and as each layer is removed, its margins are studied under the microscope for the presence of cancer cells. If the margins are cancer-free, the surgery is ended.
If not, more tissue is removed, and this procedure is repeated until the margins of the final tissue examined are clear of cancer. Mohs surgery thus can eliminate the guesswork in the removal of skin cancers and pinpoint the cancer’s location when it is invisible to the naked eye.
Mohs surgery differs from other techniques since the microscopic examination of all excised tissues during the surgery eliminates the need to “estimate” how far out or deep the roots of the skin cancer go. This allows the Mohs surgeon to remove all of the cancer cells while sparing as much normal tissue as possible. In the past, Mohs was rarely chosen for melanoma surgery for fear that some microscopic melanoma cells might be missed and end up metastasizing.
In recent years, however, efforts to improve and refine the Mohs surgeon’s ability to identify melanoma cells have resulted in the development of special stains that highlight these cells. These special stains are known as immunocytochemistry or immunohistochemistry (IHC) stains and use substances that preferentially stick to pigment cells (melanocytes), where melanoma occurs, making them much easier to see with the microscope.
For example, staining excised frozen tissue sections with a melanoma antigen recognized by T cells (MART-1) effectively labels/locates the melanocytes, helping to home in on melanomas. The MART-1-stained sections are processed and evaluated for the presence of tumor in the margins; certain signs such as nests of atypical melanocytes show that the margins are positive for melanoma and that further surgery must be done. If none of these signs are present, the surgery is concluded. Thanks to such advances, more surgeons are now using the Mohs procedure with certain melanomas.