DS20: Melanoma in situ and lentigo maligna: a need to optimize excision margins

Richard Barlow and Ure Eke

University Hospital Coventry and Warwickshire, Coventry, UK

The National Institute for Health and Care Excellence guidelines recommend a 5-mm clinical margin to ensure a 97% cure rate for stage 0 melanoma, lentigo maligna (LM) and melanoma in situ (MIS). We undertook a retrospective audit of all excised LM and MIS in a single centre between 2008 and 2017. One hundred cases of LM and 65 cases of MIS were identified within this period. Histopathology reports, clinic letters and operating notes were used to confirm excision margins and recurrences. The average age of patients with MIS at the time of diagnosis was 62 years (range 28·9–90·9). Fifty of 65 patients with MIS underwent excision biopsy in the first instance, with 2-mm margins; 47 of these were performed by a dermatologist and three by plastic surgeons. The mean histological clinical margin was 1·95 mm. Only six of 50 underwent subsequent 5-mm wide local excision (WLE), none of which demonstrated any residual lesion. Ten of 50 of the 2-mm margin excisional biopsied MIS were located on the head and neck, while 40/50 were on the trunk and limbs. The remaining 15/65 cases had a preceding punch or incisional biopsy, one of which was located on the head and neck. Thirteen of these cases underwent 5-mm WLE, while the other two had 2-mm margin excisions. The mean histological radial margin was 2·92 mm. There were no recorded recurrences for any of the cases of MIS (100%). The average duration of follow-up was 9 years (range 5·1–13·4). The average age of patients with LM at the time of diagnosis was 73 years (range 45·4–90·8) and the average duration of follow-up was 8·2 years (range 5–13). Thirty-five cases of LM were excluded from follow-up as they had died before the end of a 5-year follow-up period. A total of 18/100 (18%) had at least one local recurrence within a mean time of 5·5 years (range 2–9). Of these recurrences, 15 (83%) had undergone WLE with 5-mm margins, two (11%) had excision biopsy with a 2-mm margin only and one (5%) had 3-mm WLE due to location on lower eyelid. Sixteen of 18 (89%) were of the head and neck, while the other two were sited on the back and big toe. In summary, there were no recurrences in any cases of MIS, the majority of which underwent 2-mm margin excisions. For LM on the head and neck area, there was an 18% recurrence rate, with the majority of these cases occurring despite a 5-mm WLE. These results suggest that while closely related histologically, these conditions behave very differently clinically and a revision of national guidance on excision margins is required.