Seborrheic Keratosis-Like Melanoma: Novel Insights Into Clinical, Dermoscopic, and Reflectance Confocal Microscopy Diagnosis of an Atypical Melanoma Variant

Background: Studies have found that few lesions clinically diagnosed as seborrheic keratosis (SK) revealed Cutaneous melanoma (CM) on histopathology. When CM mimics SK, they are defined as seborrheic keratosis-like melanoma (SKLM), and a delayed diagnosis and treatment can occur. Methods: We conducted a retrospective descriptive, monocentric study of the epidemiological, clinical, videodermoscopy (VDS), and reflectance confocal microscopy (RCM) characteristics of histopathologically proven SKLM diagnosed between 2018 and 2024. Results: The study population consisted of 60 patients: 44 males (73.3%) and 16 females (26.7%) with lesions located in 73.3% of cases on the trunk. Concerning histological type, superficial spreading melanoma was the more frequent (86.7%). More than 50% of tumors had a Breslow thickness <0.8 mm. The findings from the VDS examination using the revised Argenziano Seven Point Checklist revealed that 100% of cases presented at least one dermoscopic melanoma-specific criterion and, for this reason, had an indication for surgical excision. Typical RCM patterns associated with melanoma diagnosis were observed, including irregular honeycomb/cobblestone pattern (82.1%), irregular DEJ nests (78.6%), dermal inflammation (53.6%), irregular dermal nests (53.6%), dendritic cells in sheets/tangled lines (50%), and atypical round cells (39.3%). Conclusion: Our study provides valuable insights into the dermoscopic, RCM, and histological features of SKLM based on the largest monocentric cohort. The distinctive dermoscopic patterns, along with the confocal features, aid in the differentiation from other pigmented lesions.