Adamantinoma-like ewing family tumors of the head and neck: A pitfall in the differential diagnosis of basaloid and myoepithelial carcinomas

Justin A. Bishop, Rita Alaggio, Lei Zhang, Raja R. Seethala, Cristina R. Antonescu

Research output: Contribution to journalArticle

Abstract

Ewing sarcoma family tumors (EFTs) of the head and neck are rare and may be difficult to diagnose, as they display significant histologic overlap with other more common undifferentiated small blue round cell malignancies. Occasionally, EFTs may exhibit overt epithelial differentiation in the form of diffuse cytokeratin immunoexpression or squamous pearls, resembling the so-called adamantinoma-like EFTs and being challenging to distinguish from bona fide carcinomas. Furthermore, the presence of EWSR1 gene rearrangement correlated with strong keratin expression may suggest a myoepithelial carcinoma. Herein, we analyze a series of 7 adamantinoma-like EFTs of the head and neck, most of them being initially misdiagnosed as carcinomas because of their anatomic location and strong cytokeratin immunoexpression, and subsequently reclassified as EFT by molecular techniques. The tumors arose in the sinonasal tract (n=2), parotid gland (n=2), thyroid gland (n=2), and orbit (n=1), in patients ranging in age from 7 to 56 years (mean, 31y). Microscopically, they departed from the typical EFT morphology by growing as nests with peripheral nuclear palisading and prominent interlobular fibrosis, imparting a distinctly basaloid appearance. Moreover, 2 cases exhibited overt keratinization in the form of squamous pearls, and 1 sinonasal tumor demonstrated areas of intraepithelial growth. All cases were positive for CD99, pancytokeratin, and p40. A subset of cases showed synaptophysin, S100 protein, and/or p16 reactivity, further confounding the diagnosis. Fluorescence in situ hybridization assays showed EWSR1 and FLI1 rearrangements in all cases. Our results reinforce that a subset of head and neck EFTs may show strong cytokeratin expression or focal keratinization, and are therefore histologically indistinguishable from more common true epithelial neoplasms. Thus, CD99 should be included in the immunopanel of a round cell malignancy regardless of strong cytokeratin expression or anatomic location, and a strong and diffuse CD99 positivity should prompt molecular testing for the presence of EWSR1 gene rearrangements.

Original languageEnglish (US)
Pages (from-to)1267-1274
Number of pages8
JournalAmerican Journal of Surgical Pathology
Volume39
Issue number9
StatePublished - 2015

Keywords

  • Adamantinoma-like Ewing sarcoma
  • Complex epithelial differentiation
  • Ewing sarcoma family tumor
  • EWSR1
  • FLI1
  • Primitive neuroectodermal tumor

ASJC Scopus subject areas

  • Anatomy
  • Pathology and Forensic Medicine
  • Surgery

Fingerprint Dive into the research topics of 'Adamantinoma-like ewing family tumors of the head and neck: A pitfall in the differential diagnosis of basaloid and myoepithelial carcinomas'. Together they form a unique fingerprint.

  • Cite this