Morphologic and Immunophenotypic Diversity in Ewing Family Tumors

• DOI: 10.1097/01.pas.0000167056.13614.62
• Publication Date: 2021-05-10T09:26:38Z
• Authors: Andrew L Folpe; John R Goldblum; Brian P Rubin; Bahig M Shehata; Wendy Liu; Angelo P Dei Tos; Sharon W Weiss
• Keywords: CD99; CD117; Primitive neuroectodermal tumor; Immunophenotyping; Ewing's sarcoma; Adamantinoma

More than 85% of Ewing sarcoma/primitive neuroectodermal tumor (ES/PNET), or "Ewing family tumors" (EFTs), have the translocation, t (11;22) (q24;q12), with others having variant translocations. Identification these by cytogenetic and/or molecular genetic techniques is specific for EFT and increasingly recognized as "gold standard" diagnosis. However, are not universally available. We therefore studied a large group genetically confirmed EFTs to more completely understand morphologic immunophenotypic spectrum this rare sarcoma. Sixty-six cytogenetically, FISH RT-PCR proven-EFTs were retrieved. In 56 cases, immunohistochemistry (IHC) was performed pan-cytokeratins (PanCK), high weight cytokeratins (HMWCK), desmin (DES), CD99, CD117, FLI1 protein using heat-induced epitope retrieval Dako Envision system. The cases arose chiefly in children young adults (median 18 years; range, 3-65 years) both sexes (male, 32; female, 31; unknown, 3) variety bone (N = 39) soft tissue 27) sites. Histologically, 46 (73%) showed only typical features ES, 9 (16%) PNET, 3 (5%) "adamantinoma-like" features, corresponded "atypical sarcoma," principally intersecting fascicles spindled cells, 2 had abundant hyalinized matrix. IHC results follows: PanCK (18 56, 32%), HMWCK (3 55, 5%), DES (1 2%), CD99 (52 52, 100%), CD117 (13 54, 24%), (44 47, 94%). expressed EFTs, none which DES. conclusion, most, but all, can be accurately diagnosed time-honored criteria ancillary immunohistochemistry. confirmation remains essential diagnosis unusual variants EFT, including "adamantinoma-like," spindled, sclerosing, clear cell/anaplastic variants. Therefore, exclude confirm Ewing's sarcoma round cell sarcomas patterns specifically conforming known lineage (eg, rhabdomyosarcoma), cytogenetics, analysis required.