Ungual seborrheic keratosis with longitudinal melanonychia: A case report

In this paper, we report the case of a 71‐year‐old man with an 8‐year history of melanonychia on the right little finger, who referred to our hospital because the color of pigmented area had gradually darkened and the width had expanded. Physical examination revealed longitudinal melanonychia with b...

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Published inJournal of dermatology Vol. 49; no. 8; pp. 775 - 778
Main Authors Kameda, Eisuke, Togawa, Yaei, Maru, Yugo, Matsue, Hiroyuki
Format Journal Article
LanguageEnglish
Published England Wiley Subscription Services, Inc 01.08.2022
Subjects
Biopsy
Case reports
Cysts
dermoscopy
Diagnosis
Epithelium
Human papillomavirus
Hybridization
Keratosis
longitudinal melanonychia
Microscopy
milia‐like cysts
onychocytic matricoma
Skin diseases
ungual seborrheic keratosis
longitudinal melanonychia
milia-like cysts
ungual seborrheic keratosis
dermoscopy
onychocytic matricoma
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Summary:In this paper, we report the case of a 71‐year‐old man with an 8‐year history of melanonychia on the right little finger, who referred to our hospital because the color of pigmented area had gradually darkened and the width had expanded. Physical examination revealed longitudinal melanonychia with brown color (4 mm in width). Dermoscopic examination revealed multiple white round clods and splinter hemorrhages. No micro‐Hutchinson sign was observed. We performed a punch biopsy (diameter 3 mm) of the nail matrix for diagnosis. Histopathological examination revealed irregular acanthosis of epithelium of the nail bed and distal matrix, which consisted of basaloid cells without nuclear atypia. Several zones exhibited cell whorls reminiscent of squamous eddies. The whorls were composed of large pink cells arranged in an onion peel‐like fashion. The basaloid cells tested negative for human papillomavirus in situ hybridization and p16 staining. The morphology of white round clods (milia‐like cysts in metaphoric term) observed in dermoscopic analysis corresponded to squamous eddies in histopathology. Considering these features, ungual seborrheic keratosis (SK) with longitudinal melanonychia was diagnosed, which is an atypical site for SK. We suggest that the dermoscopic finding of milia‐like cysts may be useful for the diagnosis of ungual SK.
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ISSN:0385-2407
1346-8138
DOI:10.1111/1346-8138.16392