Dermatology: Practical and Conceptual Image Letter | Dermatol Pract Concept. 2025;15(4):5888 1 Hutchinson’s Sign without Melanonychia: A Key for the Diagnosis of Invasive Melanoma of the Nail Matrix Alejandra Jaramillo-Arboleda1,2, María Fernanda Torres-Calderón1,3, Francesco Piscazzi1,4,5, Maria Paz Micieli Galeazzi1,6, Llucia Alos1, Susana Puig Sardà1,7 1 Hospital Clínic de Barcelona, Universitat de Barcelona, Institut d’Investigacions Biomediques August Pi I Sunyer (IDIBAPS), Barcelona, Spain 2 Department of Dermatology, El Bosque University - Simon Bolivar Hospital, Bogotá, Colombia 3 Department of Dermatology, Instituto Dermatológico de Jalisco “Dr. José Barba Rubio”, Jalisco, Mexico 4 Dermatology Unit, IRCCS Humanitas Research Hospital, Rozzano, Milano, Italy 5 Department of Biomedical Sciences, Humanitas University, Pieve Emanuele, Milano, Italy 6 Dermatology Service, Italian Hospital of Buenos Aires, Autonomous City of Buenos Aires, Argentina 7 Centro de Investigación Biomèdica en Red de Enfermedades Raras (CIBERER), Instituto de Salud Carlos III, Barcelona, Spain Key words: Hutchinson sign, Nail matrix melanoma, Dermoscopy, Confocal Microscopy Citation: Jaramillo-Arboleda A, Torres-Calderón MF, Piscazzi F, Micieli Galeazzi MP, Alos L, Puig S. Hutchinson’s Sign without Melanonychia: a Key for the Diagnosis of Invasive Melanoma of the Nail Matrix. Dermatol Pract Concept. 2025;15(4):5888. DOI: https://doi.org/10.5826/dpc.1504a5888 Accepted: April 17, 2025; Published: October 2025 Copyright: ©2025 Jaramillo-Arboleda 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: Susana Puig, Hospital Clínic de Barcelona, Universitat de Barcelona, Institut d’Investigacions Biomediques August Pi I Sunyer (IDIBAPS), Carrer de Villarroel 170, 08036, Barcelona, Spain. ORCID ID: 0000-0003-1337-9745. E-mail: susipuig@gmail.com; spuig@clinic.cat Case Presentation A 70-year-old male presented with a recently noticed pig- mented lesion on the periungual region of the fifth finger of his right hand. Clinical examination revealed a 6 × 4 mm lesion on the proximal and lateral nailfolds, with no mela- nonychia (Figure 1). Dermoscopy showed irregular brown pigmentation and a parallel ridge pattern in the volar skin. Reflectance confocal microscopy revealed a regular honey- comb pattern, upper epidermis without atypical cells, and bright melanocytes at dermoepidermal junction (1–3 per der- mal papilla). Initial punch biopsy demonstrated melanocytic hyperplasia with mild atypia. To rule out matrix melanoma, nail matrix biopsy showed extensive melanocytic hyperpla- sia with PRAME positivity. Complete matricectomy revealed acral lentiginous melanoma with a Breslow thickness of 0.2 mm. Therapeutic margin widening surgery showed no re- sidual neoplasia, confirmed by SOX10 immunohistochemistry. Teaching Point Subungual melanoma is a rare condition, accounting for only 0.7% to 3.5% of melanoma cases [1]. Subungual melanoma often presents with a pigmented brown or black longitudinal 2 Image Letter | Dermatol Pract Concept. 2025;15(4):5888 Figure 1. Clinical examination revealed a pigmented lesion on the lateral nailfold of the fifth finger of the right hand, extending to the periungual skin, with no evidence of melanonychia (A). Dermoscopy showed irregular, asymmetrical brown pigmentation radiating into the lateral nailfold, consistent with Hutchinson’s sign (B). Reflec- tance confocal microscopy of the previously biopsied periungual skin demonstrated the honeycomb pattern of the epidermis, with the focal presence of shiny-white pagetoid dendritic cells (C) and ir- regular clusters of bright atypical dendritic cells at the dermoepider- mal junction (D). Hematoxylin and eosin staining from the biopsy confirmed a proliferation of atypical melanocytes along the basal layer, with evidence of pagetoid spread in the epidermis (E). Immu- nohistochemical staining revealed SOX10 positivity in the atypical melanocytic proliferation, further supporting the diagnosis of acral lentiginous melanoma (F). band, with irregularly pigmented lines involving 2/3 of the nail plate or the nailfolds with periungual pigmentation called Hutchinson’s sign [2]. However, this case highlights Hutchinson’s sign pigmentation of the periungual skin with- out nail plate pigmentation as an early indicator of invasive ungual melanoma, but biopsy should be performed in the nail matrix, origin of the tumor. This uncommon presenta- tion could lead to diagnostic delays, further worsening the prognosis. Clinical suspicion is critical, even in the absence of melanonychia, particularly in patients over 50 years of age. Early biopsy of the nail matrix is essential to accurate diag- nosis and timely treatment. Dermatologists should maintain a high index of suspicion for any periungual pigmentation, considering melanoma in the differential diagnosis [2]. References 1. Levit EK, Kagen MH, Scher RK, Grossman M, Altman E. The ABC rule for clinical detection of subungual melanoma.  J Am Acad Dermatol. 2000;42(2 Pt 1):269-274. DOI:10.1016/S0190 -9622(00)90137-3. PMID: 10642684 2. Benati E, Ribero S, Longo C, et al. Clinical and dermo- scopic clues to differentiate pigmented nail bands: an Inter- national Dermoscopy Society study.  J Eur Acad Dermatol Venereol. 2017;31(4):732-736. DOI:10.1111/jdv.13991. PMID: 27696528.