title: Incidental Merkel cell carcinoma in a cutaneous horn: a case report.
abstract: Merkel cell carcinoma (MCC) is a rare cutaneous neuroendocrine malignancy, which usually presents as an asymptomatic, rapidly growing, firm nodule on sun-damaged skin. We present a 93-year-old female who presented with a "cutaneous horn" on the face. On excision, histologic examination revealed a combined squamous cell carcinoma in situ with underlying MCC. Merkel cell polyomavirus immunohistochemistry was negative in this lesion. This case report highlights the significant association between MCC and squamous cell carcinoma and the uncommon clinical presentation of this combined tumor in the form of a cutaneous horn.
authors.affiliation: Department of Pathology, London Health Sciences Centre and Western University, London, Ontario, Canada.
authors.forename: Brian A
authors.initials: BA
authors.lastname: Schick
authors.affiliation: Schulich School of Medicine & Dentistry and Western University, London, Ontario, Canada.
authors.forename: Joshua S
authors.initials: JS
authors.lastname: Tobe
authors.affiliation: Department of Pathology, London Health Sciences Centre and Western University, London, Ontario, Canada.
authors.forename: Mariamma G
authors.initials: MG
authors.lastname: Joseph
authors.affiliation: Department of Pathology, Huron Perth Healthcare Alliance, Stratford General Hospital, Stratford, Ontario, Canada.
authors.forename: Tyler B
authors.initials: TB
authors.lastname: Rouse
authors.affiliation: Department of Pathology, London Health Sciences Centre and Western University, London, Ontario, Canada.
authors.forename: Manal Y
authors.initials: MY
authors.lastname: Gabril
keywords: Merkel cell carcinoma; cutaneous horn; squamous cell carcinoma