UNASSIGNED: @entity2828 ( @entity2828 ) 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 @entity5 . Occasionally, @entity2828 may exhibit overt epithelial differentiation in the form of diffuse cytokeratin immunoexpression or squamous pearls, resembling the so-called @entity7197 -like @entity2828 and being challenging to distinguish from bona fide @entity189 . Furthermore, the presence of @entity12726 gene rearrangement correlated with strong keratin expression may suggest a @entity189 . Herein, we analyze a series of 7 @entity7197 -like @entity2828 of the head and neck, most of them being initially misdiagnosed as @entity189 because of their anatomic location and strong cytokeratin immunoexpression, and subsequently reclassified as EFT by molecular techniques. The @entity5 arose in the sinonasal tract (n=2), parotid gland (n=2), thyroid gland (n=2), and orbit (n=1), in @entity1 ranging in age from 7 to 56 years (mean, 31 y). Microscopically, they departed from the typical EFT morphology by growing as nests with peripheral nuclear palisading and prominent interlobular @entity82 , imparting a distinctly basaloid appearance. Moreover, 2 cases exhibited overt keratinization in the form of squamous pearls, and 1 sinonasal @entity5 demonstrated areas of intraepithelial growth. All cases were positive for @entity3778 , pancytokeratin, and @entity4666 . A subset of cases showed @entity5473 , @entity2281 protein, and/or @entity986 reactivity, further confounding the diagnosis. Fluorescence in situ hybridization assays showed @entity12726 and @entity21468 rearrangements in all cases. Our results reinforce that a subset of head and neck @entity2828 may show strong cytokeratin expression or focal keratinization, and are therefore histologically indistinguishable from more common true @entity2785 . Thus, @entity3778 should be included in the immunopanel of a round cell malignancy regardless of strong cytokeratin expression or anatomic location, and a strong and diffuse @entity3778 positivity should prompt molecular testing for the presence of @entity12726 gene rearrangements.

XXXX -like Ewing Family Tumors of the Head and Neck: A Pitfall in the Differential Diagnosis of @entity189 .

@entity1 :: ('9606', 'Species') :: ['patients'] @entity2828 :: ('MESH:D012512', 'Disease') :: ['Ewing sarcoma family tumors', 'EFTs'] @entity82 :: ('MESH:D005355', 'Disease') :: ['fibrosis'] @entity7197 :: ('MESH:D050398', 'Disease') :: ['adamantinoma'] @entity5473 :: ('6855', 'Gene') :: ['synaptophysin'] @entity4666 :: ('3578', 'Gene') :: ['p40'] @entity986 :: ('1029', 'Gene') :: ['p16'] @entity5 :: ('MESH:D009369', 'Disease') :: ['tumor', 'tumors', 'malignancies'] @entity2785 :: ('MESH:D009375', 'Disease') :: ['epithelial neoplasms'] @entity189 :: ('MESH:D002277', 'Disease') :: ['myoepithelial carcinoma', 'carcinomas'] @entity3778 :: ('4267', 'Gene') :: ['CD99'] @entity21468 :: ('2313', 'Gene') :: ['FLI1'] @entity12726 :: ('2130', 'Gene') :: ['EWSR1'] @entity2281 :: ('6271', 'Gene') :: ['S100']
@entity7197 :: (MESH:D050398,Disease) :: ['Adamantinoma']
