The differential diagnosis of lichenoid keratosis and seborrheic keratosis with reflectance confocal microscopy: a preliminary study.

BACKGROUNDS AND OBJECTIVES: Lichenoid keratosis (LK, or lichen planus-like keratosis, LPLK) and seborrheic keratosis (SK) present as similar benign keratotic lesions on cosmetically sensitive area, but require different therapies. Both lesions can be easily differentiated based on histological evaluation of biopsy materials. However, the biopsies may cause scarring and result in hyper-pigmentation, which reduces the compliance of the patients to be treated. In this study, we investigated the role of reflectance confocal microscopy (RCM) in the non-invasive differential diagnosis of LK and SK. PATIENTS AND METHODS: Cases with facial brown patches or plaques suspicious of SK were enrolled in the study. After written informed consent was obtained, the lesions were photographed, imaged by RCM, and then biopsied. The RCM findings were analyzed and correlated with histology results. Evaluation of the RCM pictures and confirmation with histological results were conducted by two independent dermatologists. RESULTS: In total, 10 cases were enrolled in the study. The main characteristics of LK lesions observed by RCM were the disarray of the dermal-epidermal junction (DEJ), and marked inflammatory infiltrates in the superficial dermis; while prominent cerebriform pattern, or elongated cords with bulbous projections without significant inflammation reaction, were the features of SK. Among the 10 cases, clinically suspicious of facial SK, 4 were determined as LK, 6 as SK by RCM imaging, and all the RCM findings were confirmed by histological results. CONCLUSIONS: The RCM features of LK and SK have significant difference, highlighting the important role of RCM in the differential diagnosis of LK and SK, avoiding biopsies and allowing safe treatments.