Dermatology: Practical and Conceptual Research Letter | Dermatol Pract Concept. 2025;15(2):4815 1 Optical Super-High Magnification Dermoscopy of Solar Lentigo and Lichen Planus-Like Keratosis Joanna Pogorzelska-Dyrbuś1, Dorota Ławniczak-Cielińska2, Elisa Cinotti3 1 “Estevita” Specialist Medical Practice, Tychy, Poland 2 Department of Pathomorphology, Provincial Specialist Hospital Megrez, Tychy, Poland 3 Dermatology Unit, Department of Medical, Surgical and Neurological Sciences, University of Siena, Siena, Italy Key words: Histopathology, Lichen planus-like keratosis, Optical super-high magnification dermoscopy, Solar lentigo Citation: Pogorzelska-Dyrbuś J, Ławniczak-Cielińska D, Cinotti E. Optical Super-High-Magnification Dermoscopy of Solar Lentigo and Lichen Planus-Like Keratosis. Dermatol Pract Concept. 2025;15(2):4815. DOI: https://doi.org/10.5826/dpc.1502a4815 Accepted: October 8, 2024; Published: April 2025 Copyright: ©2025 Pogorzelska-Dyrbuś et al. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial License (BY-NC-4.0), https://creativecommons.org/licenses/by-nc/4.0/, which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original authors and source are credited. Funding: None. Competing interests: None. Authorship: All authors have contributed significantly to this publication. Corresponding author: Joanna Pogorzelska-Dyrbuś, MD PhD “Estevita” Specialist Medical Practice, 43-100 Tychy, Silesia, Poland. ORCID ID: 0000-0001-6989-0273. E-mail: jpogorzelskadyrbus@gmail.com, phone: +48 32 227 96 30 Introduction Solar lentigo (SL) and lichen planus-like keratosis (LPLK) are common hyperpigmentation disorders, frequently occur- ring on the sun-exposed areas of the skin in the middle-aged and elderly population. Although benign, they can clinically and even dermoscopically mimic melanoma. Due to the pos- sibility of obtaining an up to 400x magnification, optical super-high magnification dermoscopy (OSHMD) enables observation of individual cells, including assisting in dif- ferentiating between keratinocytes and melanocytes. Thus, OSHMD can be a helpful modality, especially in problematic dermoscopy cases [1]. Case Presentations A 73-year-old woman presented with a pigmented mac- ule of the left cheek. Dermoscopy revealed light brown homogenous pigmentation with brown circles around the follicular openings (Figure 1A). OSHMD revealed clearly visible brown-reddish uniform polygonal structures corre- sponding to keratinocytes that contoured follicular openings (Figures 1B and C). Moreover, feature typically found in standard dermos- copy and labelled “moth-eaten” borders, in OSHMD con- sisted of areas of dense arrangement of brown polygonal structures with well-defined borders (Figure 1C). After bi- opsy, the diagnosis of SL was confirmed histopathologically (Figure 1D). A 55-year-old woman presented with a dark brown-gray macule of the right arm. Dermoscopy revealed gray-brown dots distributed on a structureless light brown background (Figure 2A) that corresponded in OSHMD to melanophages, visible as numerous out-of-focus blue-purple large struc- tures (Figure 2B). Moreover, straight linear vessels were also 2 Research Letter | Dermatol Pract Concept. 2025;15(2):4815 Figure 1. Solar lentigo (SL) image in standard and optical super-high magnification dermoscopy (OSHMD) and histopathology. (A) A brown homogenous pigmentation with brown circles around follicular openings in standard dermoscopy (20x magnification). (B) Follicular opening surrounded by polygonal structures corresponding to keratinocytes, indicated by black arrows in OSHMD (400x magnification). (C) “Moth-eaten” structures visible in OSHMD, consisting of a dense ar- rangement of brown polygonal structures indicated by black arrows (400x magnification). (D) Histopathology image of the SL, demonstrating pigmented keratinocytes of the basal layer. All dermoscopy images taken with Medicam 1000 (FotoFinder Systems GmbH). visible. Histopathology of the lesion confirmed the dermo- scopic diagnosis of LPLK (Figure 2C). Due to the significant overlap of standard dermoscopy features, diagnosing flat pigmented lesions of the face is chal- lenging. New imaging modalities like OSHMD or line-field confocal optical coherence tomography (LC-OCT) may vi- sualize important diagnostic details, therefore enabling their differentiation [2]. Dermoscopic features of solar lentigo are the presence of sharply demarcated borders and homogenous brown pigmentation sparing adnexa. LPLK, which corresponds to SL in regression phase, can be without dermoscopic features of a pre-existing lesion, and due to the presence of gray dots, may raise suspicion of melanoma with regression. OSHMD findings in SL corresponded to expected histo- logical features, with hyperpigmented keratinocytes [3]. The thickening and pigmentation of the epidermis, which is char- acteristic of SL, is most likely due to the enlargement and discoloration of individual keratinocytes which accumulated the melanin pigment [3, 4]. Research Letter | Dermatol Pract Concept. 2025;15(2):4815 3 Figure 2. Lichen planus-like keratosis (LPLK) in standard and optical super-high magnification dermoscopy and histopathology. (A) Gray dots homogeneously distributed on a structureless light brown background in standard dermoscopy (20x magnification). (B) Numerous out-of-focus blue-purple structures indicated with asterisks, and a straight linear vessel indicated with a black arrow (400x magnification). (C) Histopathology image of the LPLK with melanophages indicated by the red arrows. All dermoscopy images taken with Medicam 1000 (FotoFinder Systems GmbH). LPLK is characterized by inflammation and regression of a pre-existing lesion. OSHMD showed melanophages, what explains the origin of black dots visible in standard dermos- copy [5]. Conclusions Because OSHMD provides more detailed features, which to some degree correspond to histopathology, it allows for a better understanding of the structures visible in standard dermoscopy. Thanks to the detailed depiction of individual cells in the described lesions, OSHMD can be useful for the diagnosis of SL and LPLK in daily practice [6]. References 1. Cinotti E, Rossi R, Ferrara G, Tognetti L, Rubegni P, Perrot JL. Super-high magnification dermoscopy can identify pigmented cells: correlation with reflectance confocal microscopy. Br J Dermatol. 2019;181(1):e1. DOI: 10.1111/bjd.17781. PMID: 31259403. 2. Cappilli S, Tognetti L, Di Stefani A, et al. Line-field confocal op- tical coherence tomography (LC-OCT) for the assessment of flat 4 Research Letter | Dermatol Pract Concept. 2025;15(2):4815 5. 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