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Minimum excision margins suggested for skin cancer
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When Mohs micrographic surgery is not a treatment option for nonmelanoma skin cancer, a minimum of 5-mm margins for low-risk lesions should be observed with conventional excision to ensure 95% confidence of complete removal, according to study results.
Researchers conducted a retrospective review of 299 patients (mean age, 68 years; 180 men) with nonmelanoma skin cancer (NMSC) of the face treated with Mohs micrographic surgery (MMS) from 2005 to 2011 at the University of Virginia Health System. Size and final defect size were compared to determine necessary margins. Histological characteristics were used to categorize all lesions. Four hundred ninety-five lesions (337 in men) were accurately measured and studied.
Mean margins for low-risk basal cell carcinomas (BCC) and high-risk BCC were 2.4 mm and 3.7 mm, respectively; for low-risk squamous cell carcinomas (SCC) and high-risk SCC, mean margins were 2.6 mm and 5.3 mm, respectively.
There were statistical differences in surgical margins between all low- and high-risk cancer types. Larger margins showed no association with established high-risk zones for BCC and SCC. The necessary margins to ensure complete excision of 95% of all lesions were 4.75 mm for low-risk BCC, 8 mm for high-risk BCC, 5 mm for low-risk SCC and 13.25 mm for high-risk SCC.
“High-risk NMSC lesions of the face are best treated with MMS based on the larger mean surgical margins and the greater variability found among them,” the researchers concluded. “There may be circumstances in which MMS is not available or practical, and conventional excision with formalin pathology must be performed.
“This study suggests that a minimum of 5-mm margins should be observed for even the low-risk NMSC in order to capture a 95% confidence of complete excision. High-risk lesions require closer to 1-cm margins, especially the large, poorly differentiated SCC.”
Disclosure: The researchers report no relevant financial disclosures.
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