Retro- and prospective histologic and immunohistochemical analysis of safety margins following complete excision of less than 1 mm melanomas.

Reexcisions for melanoma do rarely present residual melanoma. To analyze the number of positive margins in reexcisions of in situ and <1 mm melanomas. To see whether the immunohistochemical (IHC) panel (Preferentially expressed antigen of melanoma (PRAME), Sry-related HMg-Box gene 10 (SOX 10), Human melanoma black 45 (HMB45), and Melan A) detected additional cases of melanoma. Three pilot cohorts (retrospective, prospective, and direct safety margins) were analyzed on the persistence of melanoma in reexcisions. Among the 97 cases of the retrospective cohort (27 in situ and 69 invasive melanomas), one residual in situ melanoma was detected in the reexcisions. In the second cohort, among 81 cases (18 in situ and 63 invasive melanomas), two cases (2.5%) presented in situ melanoma. In the group where direct margins were taken ( n  = 21) 2 (9.5%) in situ melanoma were evidenced in the margins. The IHC panel was needed to confirm three additional in situ melanomas in cohort 2. In a total of 178 cases (97 + 81) of reexcision, three and five cases (1.7 and 3.4%) of in situ melanoma were evidenced after H/E and IHC, respectively. These pilot data could question the usefulness of reexcision in <1 mm melanomas, particularly as only cases of in situ melanoma were detected. Larges prospective series would be required to answer this issue.