Demographic and Tumor Characteristics of Lentigo Maligna and Lentigo Maligna Melanoma for Presurgical <scp>RCM</scp> Mapping: A Retrospective Study

Head and neck lentigo maligna (LM) and lentigo maligna melanoma (LMM) pose surgical challenges due to frequent subclinical extension and their location in sensitive areas [1, 2]. Preoperative reflectance confocal microscopy (RCM) has become a valuable tool to better delineate peripheral margins and identify occult invasion, reducing the number of surgical stages required for staged excision (SE) [1, 3]. Despite expanding use, little is known about which lesions are most commonly selected for RCM mapping. We aimed to compare demographic and tumor characteristics of LM/LMM referred for RCM mapping with those managed without RCM mapping. A retrospective study (2004–2014) was conducted in which treating surgeons, based on clinical and dermoscopic examination, determined whether patients with biopsy-proven LM/LMM underwent RCM mapping before SE, reflecting real-world practice at a tertiary referral center. Demographic and tumor characteristics were collected, and border definition and regularity were assessed from dermoscopic images across four quadrants. If a shave biopsy removed > 50% of the lesion, available clinical images were used to supplement border assessment. RCM evaluation included VivaScope 1500 examination of four orthogonal margins until normal epidermis was reached and VivaScope 3000 assessment for invasiveness using established criteria: epidermal/junctional disarray, large, atypical melanocytes, and melanocytic nests [1]. Statistical analyses included t-tests and chi-square tests. A total of 258 patients were included: 141 underwent presurgical RCM mapping and 117 did not (Table 1). Mean age was similar between groups (~68 years). Women were more frequently referred for RCM mapping (48.9% vs. 28.2%, p = 0.001). Most cases represented stage 0 LM in both groups. Amelanotic lesions were rare and showed comparable proportions in both groups (~3%). The cheek was the most common location and was more frequent among RCM-mapped lesions (49.6% vs. 40.4%, p = 0.036). Lesions in the RCM group were larger, with a mean diameter of 16.2 mm versus 11.2 mm in the non-RCM group (p < 0.001, Figure 1). Large lesions (> 2 cm) were more common among RCM- cases (19.3% vs. 5.2%), whereas small lesions (< 10 mm) predominated in the non-RCM group (42.2% vs. 15.7%, p < 0.001). Border characteristics differed markedly: 51.8% of RCM lesions were ill-defined in all quadrants compared with only 3.4% in the non-RCM group (p < 0.001). The presence of more ill-defined borders in the RCM group was significant and consistent across all lesion quadrants (p < 0.001, Figure 1). Sensitivity analyses using multivariable logistic regression showed that ill-defined borders and larger lesion size were independently associated with referral for RCM mapping, regardless of patient age or sex. Additionally, the lesions in the RCM group were more irregular than those in the non-RCM group (Table 1). Surgeons preferentially selected larger, ill-defined, and irregular LM/LMM lesions for presurgical RCM mapping. These features are well-recognized predictors of subclinical extension and correlate with the need for wider surgical margins [4]. The findings support the notion that lesions with these characteristics may benefit most from RCM mapping, potentially allowing for fewer excision stages, more precise margins, and a personalized approach that reduces uncertainty for both patients and surgeons [3]. Notably, there are no data linking lesion size or borders to tumor invasiveness. The prominent cheek involvement may reflect its high prevalence and the technical ease of performing RCM on flat facial surfaces [1, 2]. The higher proportion of women in the RCM group may relate to cosmetic concerns, health-seeking behaviors, or provider referral patterns, although prospective studies are needed to explore this further [5]. Nonrandomized, retrospective group allocation introduces selection bias and limits outcome analysis. In conclusion, LM/LMM selected for presurgical RCM mapping at a tertiary cancer center were more likely to be larger and to display ill-defined and irregular borders. These findings suggest that such lesions may benefit most from RCM mapping. AI-Assisted Editing: Parts of this manuscript were edited for grammar, clarity, and style using ChatGPT (OpenAI, San Francisco, CA, USA). The authors reviewed and approved all AI-generated suggestions, and the final content is the authors' own. The work was supported by the National Institutes of Health/National Cancer Institute Cancer Center Support Grant P30 CA008748. The funder played no role in any aspect of the study. Reviewed and approved by Western IRB (approval 16-458). The authors declare no conflicts of interest. The data that support the findings of this study are available on request from the corresponding author.