In vivo cutaneous confocal microscopy for diagnosing the lentigo maligna spectrum: A multicentre prospective study and proposal of a lentigo maligna spectrum score.

Abstract

Cutaneous confocal microscopy (CCM) differentiates lentigo maligna (LM) from lentigo maligna melanoma (LMM) and helps characterize atypical intraepidermal melanocytic proliferation (AIMP), a potential LM precursor. However, CCM features across the LM spectrum have not been quantitatively analyzed or prospectively validated. To validate CCM features for AIMP, LM, and LMM, assess the Lentigo Maligna Score (LM) score's ability to distinguish early from invasive stages, and evaluate a novel diagnostic score. In a 4-year prospective, multicentre study, clinically suspicious LM lesions underwent CCM assessment and subsequent biopsy/excision. A blinded expert analyzed 16 CCM features and 6 LM score features. Contralateral normal skin was examined to differentiate AIMP from sun-damaged skin. A senior expert reviewed CCM-pathology discordances. Among 129 lesions (28 AIMP, 52 LM, 30 LMM, 19 benign mimickers), key CCM features distinguished LM spectrum stages. The addition of nests and dermal architectural distortion to the LM score created the LM Spectrum Score, improving diagnostic accuracy. The area under the curve increased from 0.73 (95% CI: 0.63, 0.84) to 0.95 (95% CI: 0.90, 0.99) for LMM vs LM and from 0.75 (95% CI: 0.60, 0.90) to 0.85 (95% CI :0.76, 0.95) for AIMP vs benign mimickers and sun-damaged skin. Data limited to Australian population. CCM enhances LM diagnosis and biopsy guidance. LM Spectrum Score improves accuracy but requires further validation.