Extraordinary Case ReportMyxoid Onychomatricoma—A New CasePessoa e Costa, Tomás MD*; João, Ana Luísa MD*; Pinheiro, Rita MD*; Carvalho, Rodrigo MD*; Matos Pires, Eugénia MD†; Lencastre, André MD*Author Information *Department of Dermatology and Venereology, Hospital de Santo António dos Capuchos, Centro Hospitalar de Lisboa Central, Alameda de Santo António dos Capuchos, Lisbon, Portugal; and †Department of Dermatology and Venereology, Hospital CUF Descobertas, Lisbon, Portugal. Correspondence: Tomás R. Pessoa e Costa, MD, Alameda de Santo António dos Capuchos, 1169-050 Lisbon, Portugal (e-mail: firstname.lastname@example.org). The authors declare no conflicts of interest. The American Journal of Dermatopathology: February 2020 - Volume 42 - Issue 2 - p 133-135 doi: 10.1097/DAD.0000000000001514 Buy Metrics Abstract Onychomatricoma is a slow-growing, benign neoplasm of the nail matrix with several histological variants. With only 2 cases previously reported, the term “myxoid onychomatricoma” has been used by some authors to describe a rare variant, known to have a fibromixoid component. We present a case of a 51-year-old Caucasian woman with a 1-year history of thickening and discoloration of the right thumbnail, who was initially misdiagnosed as onychomycosis. After performing a magnetic resonance imaging that showed a tumor with several filamentous projections, an onychomatricoma was suspected and a total distal plaque avulsion was performed. Histology revealed a biphasic tumor with an epithelial component and a prominent myxoid stroma. Immunohistochemical staining was then used, confirming the diagnosis. Considering these findings, we believe that our case meets the diagnostic description of “myxoid onychomatricoma” and is, therefore, a new case of this rare histological variant. Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.