Monday, September 25, 2006
More than one out of every seven Americans will contract some kind of skin cancer in the course of his or her lifetime. Intense or prolonged exposure to the sun's ultraviolet rays is the number one cause of skin cancer. So as we exit another summer and enter into another ski season with our favorite toys, a little information may be useful
Non-melanoma skin cancers, basal cell cancer and squamous cell cancer, are usually treated with a dose of cold steel excisional biopsy. Those cancers are fairly slow growing and rarely spread. If all the cancer is removed with excision, there is a low rate of recurrence.
Optimally, all of the cancerous tissue is excised with as little surrounding normal tissue as possible except as needed for a cosmetically acceptable surgical wound closure. In order to determine the completeness of excision of the cancer at the time of the excision, the doctor can employ the services of a pathologist to perform frozen sections of a specimen.
For frozen section diagnosis and assessment of surgical margins, the excision specimen is delivered to the pathologist immediately after removal from the patient. The pathologist then applies various colors of ink to the surgical margins and freezes the specimen quickly in a device called a cryostat. Once the specimen is frozen, the pathologist cuts thin sections on a microtome in the cryostat, mounts the sections on glass slides, stains the slides with routine frozen section stains, and then examines the stained slides under a microscope. This examination reveals the type of cancer, it's size and shape, and it's relationship to the surgical margins. This information is conveyed within minutes to the doctor doing the excision. If the cancer extends to a surgical margin, the exact location of the involved margin is communicated to the doctor who can then excise additional tissue at that time. If necessary, additional frozen sections can be performed on the re-excision specimen to assess the new surgical margins.
Depending on the site, size and shape of the excision specimen, the pathologist may employ a variety of techniques for sectioning the specimen to best evaluate the surgical margins. In many cases, excising the cancer in an ellipse of skin on a relatively flat portion of the body makes closure of the surgical defect fairly straightforward for the doctor and cosmetically satisfactory for the patient. With most small ellipses, the pathologist usually serially sections the specimen perpendicular to the surgical margins.
In many round, irregularly shaped or larger excision specimens, the pathologist may employ a technique called Mohs or modified Mohs micrographic surgery. Mohs surgery was pioneered by Frederick Mohs in the 1940's. With this technique, the pathologist orients and sections the specimen horizontal to the surface of the skin, or "en face" and the specimen can be serially sectioned from the surface to the deepest aspect of the specimen or vice versa, in order to evaluate all the surgical margins.
While the exact frozen section technique may vary depending on the nature of the specimen, the cure rates are comparable and approach 98 percent. Many of those skin cancers that do recur are felt to represent multifocal disease rather than "false negative" frozen sections. The pathologists at Yampa Valley Medical Center are well-verses and experienced in all of the frozen section techniques that may be applied to skin cancers. These frozen section services are available to any physician doing skin excisions at Yampa Valley Medical Center. If you are diagnosed with skin cancer, discuss with your physician whether you would be a candidate for excision ultilizing intraoperative frozen sections including the Mohs technique.
This column was written by MaryAnn Wall, MD,FACS Board Certified Facial and Plastic and Reconstructive Surgeon and William Cox, MD Board Certified Pathologist