P59 Results of sentinel lymph node biopsies in thin melanomas (Breslow thickness 0.8–1.0 mm) and correlation with histopathological features

Abstract

Abstract In July 2022, the National Institute for Health and Care Excellence (NICE) melanoma guidelines were updated to include recommendation for a sentinel lymph node (SLN) biopsy for those with a Breslow thickness of 0.8–1 mm and at least one of the following: ulceration, lymphovascular invasion and/or a mitotic index of ≥ 2 mm². SLN biopsy is a staging procedure and therefore has an impact on prognosis. However, SLN biopsy is an invasive procedure with associated morbidity. A 5-year retrospective review of melanoma data in the south east of Ireland was undertaken to establish the correlation between positive sentinel lymph node biopsies in 0.8–1.0-mm-thick melanomas and the risk factors outlined above. Melanoma outcomes, histopathology reports and outpatient clinic letters were assessed and data were extracted from 1 January 2018 to 31 December 2022 inclusive. A total of 52 patients were identified with a melanoma of Breslow thickness of 0.8–1 mm from the predetermined timeframe. Eight per cent (n = 4) of lesions were ulcerated. Thirteen per cent (n = 7) had a mitotic index of ≥ 2 mm². One lesion was both ulcerated and had a mitotic index of ≥ 2 mm². No lesions demonstrated lymphovascular invasion. Nineteen (36%) patients underwent SLN biopsy. All patients who underwent SLN biopsy were negative. One patient with an ulcerated melanoma did not undergo SLN biopsy and five with a mitotic index of ≥ 2 did not undergo SLN biopsy. There was no evidence of disease recurrence within the follow-up period (2 months–5 years). This population showed a 0% positivity rate on SLN biopsy. No correlation with mitotic index or ulceration and SLN biopsy was identified. No patients have developed local recurrence or metastatic disease within the follow-up period. This study supports the updated NICE guidance recommending SLN biopsies for thicker melanomas (i.e. Breslow thickness > 1.0 mm) and SLN biopsy in thinner melanomas (Breslow thickness 0.8–1 mm) only if concerning features are present on histology (i.e. ulceration, lymphovascular invasion and/or a mitotic index of ≥ 2).