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Histopathology showed onychopapilloma with onycholemmal squamous dysplasia and intracytoplasmic melanin, with Ki67-related abnormal suprabasilar nuclear staining. The case emphasizes biopsy for atypical pigmentation and growth.",{"@graph":14,"@context":73},[15,34,56],{"@type":16,"itemListElement":17},"BreadcrumbList",[18,23,27,31],{"item":19,"name":20,"@type":21,"position":22},"https://docshare.wps.com","Home","ListItem",1,{"item":24,"name":25,"@type":21,"position":26},"https://docshare.wps.com/document/","Document",2,{"item":28,"name":29,"@type":21,"position":30},"https://docshare.wps.com/document/healthcare/","Healthcare",3,{"item":32,"name":10,"@type":21,"position":33},"https://docshare.wps.com/document/pigmented-malignant-onychopapilloma-of-the-fingernail-description-of-the-string-sign/429165/",4,{"url":32,"name":10,"@type":35,"image":36,"author":41,"headline":10,"publisher":44,"fileFormat":47,"inLanguage":8,"description":12,"dateModified":48,"datePublished":49,"encodingFormat":47,"isAccessibleForFree":50,"interactionStatistic":51},"DigitalDocument",{"url":37,"@type":38,"width":39,"height":40},"https://docshare.wps.com/thumbnails/pigmented-malignant-onychopapilloma-of-the-fingernail-description-of-the-string-sign/429165.png","ImageObject",300,407,{"name":42,"@type":43},"Jiven","Person",{"url":19,"name":45,"@type":46},"DocShare","Organization","application/pdf","2026-10-31","2026-09-29",true,{"@type":52,"interactionType":53,"userInteractionCount":55},"InteractionCounter",{"@type":54},"ViewAction",12,{"@type":57,"mainEntity":58},"FAQPage",[59,65,69],{"name":60,"@type":61,"acceptedAnswer":62},"What clinical presentation suggested a “string sign” in this case?","Question",{"text":63,"@type":64},"The patient had a dark brown, firm, linear projection resembling a string arising from the nail bed near the lateral nail fold, enhanced on onychoscopy.","Answer",{"name":66,"@type":61,"acceptedAnswer":67},"What did histopathology show after nail biopsy?",{"text":68,"@type":64},"Findings were consistent with onychopapilloma, but included focal increased cellularity and squamous atypia, with intracytoplasmic melanin pigment deposition and abnormal suprabasilar nuclear staining for Ki67.",{"name":70,"@type":61,"acceptedAnswer":71},"Why is biopsy important for atypical onychopapilloma features?",{"text":72,"@type":64},"Because malignant potential was previously not recognized, the authors stress biopsy when pigmentation and growth show atypical changes that may suggest 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Rep Dermatol 2025;17:54–60 |  |\n| --- | --- |\n| DOI: 10.1159/000543433\u003Cbr>Received: May 17, 2024\u003Cbr>Accepted: December 20, 2024\u003Cbr>Published online: January 6, 2025 | © 2025 The Author(s) .\u003Cbr>Published by S. Karger AG, Basel [www.karger.com/cde](www.karger.com/cde) |\n\nThis article is licensed under the Creative Commons Attribution-NonCommercial 4.0 International License (CC BY-NC) ([http://www.karger.com/Services/OpenAccessLicense](http://www.karger.com/Services/OpenAccessLicense)). Usage and distribution for commercial purposes requires written permission.  \nCase Report  \nPigmented Malignant Onychopapilloma of the Fingernail: Description of the“String Sign”  \nRachel C. Hill a Cynthia M. Magrob Shari R. Lipner c  \naWeill Cornell Medical College, New York, NY, USA; bDepartment of Pathology, Weill Cornell  \nMedicine, New York, NY, USA; cDepartment of Dermatology, Weill Cornell Medicine, New York, NY, USA  \nKeywords  \nOnychopapilloma · Malignant onychopapilloma · Pigmented onychopapilloma  \nAbstract  \nIntroduction: Onychopapillomaisa benign nail tumor of the nail bed and distal matrix that typically presents as isolated longitudinal erythronychia on clinical examination. In 2021, Haneke et al. [JCutan Pathol. 2021;48(1):174–9] described the 1st case of a malignant variant of onychopapilloma. Case Presentation: We present the case of a 34-year-old female patient, Fitzpatrick type V, who presented to our specialty outpatient nail clinic with a 10-year history of a pigmented growth on the lateral nail fold of the left 3rd fingernail that resembled a string. On histopathology, the patient’s biopsy showed significant onycholemmal squamous dysplasia with intracytoplasmic melanin pigment deposition in a background of onychopapilloma; concurrent abnormal suprabasilar nuclear staining amidst keratinocytes for Ki67 was observed. Conclusion: The proportion of onychopapilloma cases that develop malignant potential is currently unknown, as onychopapillomas were believed to be entirely benign until 2021. Malignant onychopapilloma often presents with longitudinal melanonychia in patients with skin of color and with longitudinal erythronychia inpatients with lighter phototypes. Our case highlights the importance of performing a biopsy inpatients who present with atypical features of onychopapilloma, including changes in pigmentation and growth, the latter potentially presenting with the “string sign ”  \n© 2025 The Author(s) .  \nPublished by S. KargerAG, Basel  \nIntroduction  \nOnychopapilloma, 1st described by Baran and Perrin [1] in 1995 as “localized multinucleate distal subungual keratosis,” is a benign nail tumor of the nail bed and distal matrix that typically appears as isolated longitudinal erythronychia on clinical  \nCorrespondence to:  \nShari R. Lipner, [shl9032](shl9032@ med.cornell.edu)[@](shl9032@ med.cornell.edu)[ med.cornell.edu](shl9032@ med.cornell.edu)  \nCase Reports in Dermatology  \nCase Rep Dermatol 2025;17:54–60 55  \n\n| DOI: 10.1159/000543433 | © 2025 The Author(s) . Published by S. Karger AG, Basel [www.karger.com/cde](www.karger.com/cde) |\n| --- | --- |\n\nHill et al.: Pigmented Malignant Onychopapilloma  \nexamination [1–4] . Less common clinical presentations include longitudinal leukonychia, longitudinal melanonychia, and long or short splinter hemorrhages [5, 6] . The thumb is most frequently affected, although any digit may be involved [5] . On physical and onycoscopic examination, a distal, subungual, hyperkeratotic mass may be appreciated, and was reported in 100% of 47 histologically confirmed onychopapillomas in a retrospective cases series by Tosti et al. [5] . Onychopapilloma usually arises in the 5th decade of life, although patients of any age can be affected [7] . In general, an onychopapilloma with classic clinical features that is stable and asymptomatic may be monitored. In 2021, Haneke et al. [8] reported the 1st case of a malignant variant of onychopapilloma, which presente","cbCaicfs6zQwnugC","https://ap.wps.com/l/cbCaicfs6zQwnugC","pdf",653154,"English","# Introduction\n# Case Report\n## Physical Examination and Differential Diagnosis\n## Procedure and Histopathology\n# Conclusion","[{\"question\":\"What clinical presentation suggested a “string sign” in this case?\",\"answer\":\"The patient had a dark brown, firm, linear projection resembling a string arising from the nail bed near the lateral nail fold, enhanced on onychoscopy.\"},{\"question\":\"What did histopathology show after nail biopsy?\",\"answer\":\"Findings were consistent with onychopapilloma, but included focal increased cellularity and squamous atypia, with intracytoplasmic melanin pigment deposition and abnormal suprabasilar nuclear staining for Ki67.\"},{\"question\":\"Why is biopsy important for atypical onychopapilloma features?\",\"answer\":\"Because malignant potential was previously not recognized, the authors stress biopsy when pigmentation and growth show atypical changes that may suggest malignancy.\"}]","Pigmented Malignant Onychopapilloma of the Fingernail - Description of the “String Sign” | PDF",1790648882,18]