Dermatologic surgery
Surgical margins for melanoma in situ

Presented as a Tromovitch Award Finalist at the American College of Mohs Surgery Annual Meeting in Austin, TX, on April 23, 2009.
https://doi.org/10.1016/j.jaad.2011.06.019Get rights and content

Background

A controversy in the treatment of melanoma in situ is the required width of surgical margin. The currently accepted 5-mm margin is based on a 1992 consensus opinion, despite data since then showing this is inadequate.

Objective

We sought to develop guidelines for predetermined surgical margins for excision of melanoma in situ.

Methods

A prospectively collected series of 1072 patients with 1120 melanoma in situs was studied. All lesions were excised by Mohs micrographic surgery with frozen-section examination of the margin. The minimal surgical margin was 6 mm, and the total margin was calculated by adding an additional 3 mm for each subsequent stage required. The minimum surgical margin that would successfully remove 97% of all tumors was calculated. Local recurrence was also tabulated.

Results

In all, 86% of melanoma in situs were successfully excised with a 6-mm margin; 9 mm removed 98.9% of melanoma in situs. The superiority of 9-mm to 6-mm margins was significant (P < .001). Gender, location, and diameter did not affect results. Recurrence rate for this set of patients treated with Mohs micrographic surgery was 0.3% (n = 3).

Limitations

Margins less than 6 mm were not studied. This is a referral center for melanoma in situ and 10% of tumors were previously treated before presentation to our clinic.

Conclusion

The frequently recommended 5-mm margin for melanoma is inadequate. Standard surgical excision of melanoma in situ should include 9 mm of normal-appearing skin, similar to that recommended for early invasive melanoma.

Section snippets

Methods

A prospective database of all patients referred for Mohs excision of melanoma began in 1982, and records various patient and tumor characteristics. All patients with biopsy-proven primary melanoma in situ from March 1982 through September 2008 were considered for this study. Patients without follow-up were excluded.

All patients were treated with Mohs micrographic surgery, which was initiated by excising the biopsy site or remaining visible tumor with 3 mm of normal-appearing skin to adipose

Patient and lesion characteristics

From 1982 to 2008, 1246 consecutive patients were treated for primary melanoma in situ. In all, 174 patients (14%) had no follow-up and were excluded, usually because they were treated toward the end of the accrual period. The final cohort comprised 1072 patients with 1120 melanoma in situs. Of patients, 60% were men and the mean age was 65 years (SD 15). Most tumors were located on the face and clinical diameter was variable (Table I). Although the mean tumor diameter was 2.8 cm, 73% of all

Validity of frozen-section interpretation of melanoma

Both the low recurrence rate and the ability to achieve narrow margins (<1 cm) in 99% of patients support the accuracy of frozen sections and refute concerns that frozen sections cannot adequately detect melanoma at the margins. If our diagnostic criteria were too strict or if melanomas were not visible by frozen section, we would underdiagnose melanoma and expect a high recurrence rate. Instead, our recurrence rate was 0.3%. If our diagnostic criteria were too liberal and we excised

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    Funding sources: None.

    Conflicts of interest: None declared.

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