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Surgical margins for standard excision should include 9 mm of normal-appearing skin for melanoma in situs, according to a recent study.
Pittsburgh - A recent study demonstrates that larger margins than the frequently recommended 5 mm are required for excising lentigo maligna melanoma and melanoma in situ, according to Joy H. Kunishige, M.D., co-author of the study and a dermatologist in private practice in Pittsburgh.
"Our recent study (currently submitted for publication) looked at melanoma in situ with 6 mm margins - most surgeons do 5 mm - and we found that 14 percent of patients still had tumors at that edge.
"However, 9 mm margins would give the dermatologist a 99 percent cure rate," Dr. Kunishige says.
Melanoma in situ
"With lentigo maligna and melanoma in situ, what you see can be just the tip of the iceberg.
"Frequently, there is still tumor 6 mm or 1 cm or even 2 cm beyond the edge of the visible lesion," Dr. Kunishige says.
Historically, melanoma in situ has been treated with excision of the brown patch and about a 5 mm extra of normal-appearing skin. "That is the current standard. Those simple excisions with 5 mm margins have about an 80 percent recurrence rate, which is related to 5 mm margins not clearing the entire tumor 10 to 50 percent of the time. The current standard is not adequate," she says.
In addition, today, dermatologists are increasingly treating melanoma in situ and inadequate treatment frequently leads to recurrence as invasive melanoma.
Dr. Kunishige and her colleagues John A. Zitelli, M.D., and David G. Brodland, M.D., propose that the guideline should be reviewed in light of new evidence since the 1992 consensus, which was accepted without the support of controlled medical studies.
Their recent study set out to develop evidence-based guidelines for predetermined surgical margins for excision of melanoma in situ.
The prospectively collected series of 1,070 consecutive patients with 1,120 melanoma in situs was studied. All lesions were excised by means of fresh tissue technique of Mohs micrographic surgery with frozen section examination of the margin. (After 2003, MART-1 immunostains were used.)
The minimal surgical margin was 6 mm, and the total margin was calculated by adding additional 3 mm for each subsequent stage to remove the tumor completely.
"We found that 84.96 percent of melanoma in situs was successfully excised with a 6 mm margin. However, 9 mm removed 98.9 percent of melanoma in situs. Location and clinical diameter did not change the efficacy associated with each margin," Dr. Kunishige says.
The researchers concluded that the predetermined surgical margins for standard surgical excision should include 9 mm of normal-appearing skin for melanoma in situs. Required width of surgical margins for melanoma in situ is similar to that recommended for early invasive melanoma.
According to the results of the study, "We think 9 mm is sufficient, but it could be 8 mm, it could be 1 cm. We need to keep doing studies, but we recommended 9 mm at this time," Dr. Kunishige says.
Some surgeons note that the larger margins take unnecessary tissue to err on the side of caution. Dr. Kunishige agrees, but says she does not feel comfortable leaving tumor in 14 percent of patients, especially with data that shows it can recur as invasive melanoma.
If smaller margins are desired, for cosmesis or function, Mohs surgery can be used to keep the margins exactly as narrow as the tumor. One caveat is that it is technically difficult to make and read the slides.However, with training, it can be done, and the efficacy of Mohs is supported by very low recurrence rates. Recurrence rate was 0.3 percent in the study.
The other treatment options - aside from excision and Mohs surgery - are not commonly used, Dr. Kunishige says. Other treatments include Aldara (imiquimod, Graceway), interferon injections or cryotherapy, but are usually limited to patients who are not surgical candidates and who understand the risks. DT