DS07 Surgical treatment for melanoma <i>in situ</i> and lentigo maligna: the impact of changing policy on wider excisions after adequate histological clearance

Abstract Lentigo maligna (LM) and melanoma in situ (MIS) are ‘stage 0’ melanomas, often characterized as precancerous changes to melanocytes with potential to develop into invasive melanoma. As noted in the 2010 British Association of Dermatologists melanoma guidelines, ‘LM and other in situ melanomas have no potential for metastatic spread and the aim should be to excise the lesion completely with a clear histological margin, although margin size remains undefined. No further treatment is then required.’ To achieve this, a 5-mm surgical margin was advised, and this is reflected as a ‘consider’ recommendation in the 2022 National Institute for Health and Care Excellence guidance. However, most atypical, pigmented lesions on the trunk and limbs and some on the head and neck are initially excised with a narrow margin excision (NME) to determine presence of invasion. The need for wider excision if there is adequate histological clearance for MIS and LM is unclear and not specified in current guidance. Historically in our centre, all cases of LM and MIS have undergone a 5-mm wide excision following NME irrespectively of reported margins. In January 2024, we implemented a change to only offer wide local excision (WLE) if the histological margin for MIS was &amp;lt; 2 mm or for LM &amp;lt; 3 mm on the NME. This was based on review of current evidence and the impact of potentially unnecessary surgery vs. the very low risk of recurrence. All cases were discussed at a multidisciplinary team with a review of the histology and a final decision made, considering patient age, comorbidities and performance status. We assessed the impact on WLE rates since implementation 12 months previously. In 2024, 71 cases of LM or MIS were diagnosed (20 LM, 51 MIS). Of these, 13 (five MIS, eight LM) had an incisional biopsy, leaving 58 patients who had initial NME with reported margins. Of these, 34 were subsequently not offered WLE, who would have previously been eligible. Twenty-four were still offered a wide excision, of whom four were offered WLE despite sufficient margins, after multidisciplinary team discussion. WLE for MIS decreased by 70%. In contrast, WLE for LM was only reduced by 10%, due to higher rates of initial incisional biopsy and cases of NME not reaching 3-mm peripheral margin criteria. After implementation of this policy, WLE for melanoma with no metastatic potential has significantly decreased. Patients avoided the impact of further, potentially significant surgery, and for the National Health Service (NHS), this saved an estimated 1785 min of allocated operating time and £51 000, considering postoperative and surgical costs. This saving could be extrapolated to other departments still routinely offering WLE. We also recommend clearer national guidance to streamline practice and avoid unnecessary surgery and burden on NHS surgical waiting lists.