title: Adamantinoma-like Ewing sarcoma mimicking basal cell adenocarcinoma of the parotid gland: a case report and review of the literature.
abstract: Adamantinoma-like Ewing sarcoma (AES) is a rare variant of the Ewing family of tumors that resembles classic adamantinoma of bone. AES shows epithelial differentiation and a more complex immunohistochemical expression profile with keratin and basal marker immunoreactivity and can resemble a variety of carcinomas. We report an unusual case of an AES of the parotid gland that mimicked a basal cell adenocarcinoma. Like basal cell adenocarcinoma, this AES showed a nested basaloid proliferation with peripheral palisading in tumor nests with 'basaloid' epithelial differentiation as highlighted by cytokeratin AE1/3 and p40 positivity. However, unlike most basal cell adenocarcinomas, this tumor demonstrated high grade morphology, showed no true ductal or myoepithelial component, and also showed a tendency towards neuroectodermal phenotype with focal rosette formation, CD99 and weak synaptophysin immunoreactivity. EWSR1 and FLI1 fluorescence in situ hybridization confirmed the presence of a translocation supporting the diagnosis of AES. This is the first case of AES presenting as a primary parotid mass highlighting the potential to be mistaken for primary salivary gland carcinomas, which in addition to basal cell adenocarcinoma include other basaloid tumors such as adenoid cystic carcinoma.
authors.affiliation: Department of Pathology, University of Pittsburgh Medical Center, 200 Lothrop St, Scaife Hall A615, Pittsburgh, PA, 15213, USA, lezcanolopezm@upmc.edu.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Lezcano
authors.forename: Martha R
authors.initials: MR
authors.lastname: Clarke
authors.forename: Lei
authors.initials: L
authors.lastname: Zhang
authors.forename: Cristina R
authors.initials: CR
authors.lastname: Antonescu
authors.forename: Raja R
authors.initials: RR
authors.lastname: Seethala
mesh_terms: D000071443:12E7 Antigen; D050398:Adamantinoma / Q000473:pathology*; D000230:Adenocarcinoma / Q000175:diagnosis* / Q000473:pathology / Q000601:surgery; D015703:Antigens, CD / Q000378:metabolism; D014408:Biomarkers, Tumor / Q000378:metabolism; D015815:Cell Adhesion Molecules / Q000378:metabolism; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D053558:Keratin-3 / Q000378:metabolism; D008875:Middle Aged; D010306:Parotid Gland / Q000378:metabolism / Q000473:pathology* / Q000601:surgery; D010307:Parotid Neoplasms / Q000175:diagnosis* / Q000473:pathology / Q000601:surgery; D012512:Sarcoma, Ewing / Q000175:diagnosis* / Q000473:pathology / Q000601:surgery; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome
chemical_list: D000071443:12E7 Antigen; D015703:Antigens, CD; D014408:Biomarkers, Tumor; C061828:CD99 protein, human; D015815:Cell Adhesion Molecules; D053558:Keratin-3
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