Subungual Keratoacanthoma: A Rare Variant of Keratoacanthoma

Alexandre Miroux Catarino,Maria Goreti Catorze,Isabel Viana

doi:10.29021/spdv.76.4.922

Alexandre Miroux Catarino, Maria Goreti Catorze + Show 1 more

Open Access

https://doi.org/10.29021/spdv.76.4.922

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Abstract

Sungungual keratoacanthoma is a rare and more aggressive variant of keratoacanthoma. The authors present a case of a 49-year-old male with a one year history of a growing exophytic nodule on the nail bed of the left first toe. Physical examination revealed a two centimeters large exofitic nodule with a verrucous hyperkeratotic central area on the nail bed. A plain radiograph showed a cup-shaped lytic defect in the underlying distal phalanx. Histopathologic analysis revealed a large crater-like squamoproliferative lesion, connected to the epidermis and consisting of lobules and nests of glassy epithelium with numerous dyskeratotic cells, very little degree of cytological atypia and low mitotic activity. Lymphovascular, perineural or bone invasion were not found. Immunohistochemistry with p53 and Ki67 showed exclusive focal basal staining. The diagnosis of subungual keratoacanthoma was made. The main differential diagnosis, both clinical and histological, is with squamous cell carcinoma. It is important to consider this entity to avoid unnecessary diagnostic delays and mutilating treatments.

Highlights

Sungungual keratoacanthoma (SKA), designated solitary distal digital keratoacanthoma, is a rare and aggressive variant of keratoacanthoma
An incisional biopsy was performed and histopathology revealed a large crateriform squamoproliferative lesion (Fig. 3a), connected to the epidermis that consisted of lobules and nests of glassy epithelium with numerous dyskeratotic cells, very little cytological atypia and low mitotic activity (Fig. 3b)
SKA occurs more frequently in middle-aged and young adults, grows rapidly and becomes exophytic soon in the tumour evolution, whereas squamous cell carcinoma (SCC) is mainly observed in older patients, grows insidiously and its appearance may not suggest a tumour for a longer period

Summary

Caso Clínico

Alexandre Miroux Catarino[1], Maria Goreti Catorze[2], Isabel Viana2 1Médico Interno de Dermatovenereologia/Resident of Dermatology and Venereology, Serviço de Dermatologia, Centro Hospitalar de Lisboa Ocidental, Lisbon, Portugal 2Assistente Hospitalar Graduada de Dermatovenereologia, Serviço de Dermatologia, Centro Hospitalar de Lisboa Ocidental, Lisboa, Portugal / Consultant of Dermatology and Venereology, Dermatology Department, Centro Hospitalar de Lisboa Ocidental, Lisbon, Portugal. RESUMO – O queratoacantoma subungueal é uma variante rara do queratoacantoma, caracterizada por um comportamento mais agressivo. A radiografia óssea mostrava osteólise parcial da falange distal do respetivo dedo. Foi feito o diagnóstico de queratoacantoma subungueal. O principal diagnóstico diferencial, tanto clínico como histológico, é com o carcinoma espinocelular. The authors present a case of a 49-year-old male with a one year history of a growing exophytic nodule on the nail bed of the left first toe. Physical examination revealed a two centimeters large exofitic nodule with a verrucous hyperkeratotic central area on the nail bed. Immunohistochemistry with p53 and Ki67 showed exclusive focal basal staining. The diagnosis of subungual keratoacanthoma was made. The main differential diagnosis, both clinical and histological, is with squamous cell carcinoma.

INTRODUCTION

DISCUSSION