Adamantinoma-like Ewing Family Tumor of Soft Tissue Associated With the Vagus Nerve

Abstract

Adamantinoma-like Ewing family tumor (EFT) is a rare subset of EFTs showing mixed features of Ewing sarcoma and adamantinoma of the long bones. All currently reported cases of the adamantinoma-like type have been associated with bone. Recently, a unique type of EFT was reported showing complex epithelial differentiation associated with the vagus nerve. Here we describe another unique type of EFT arising in the soft tissue of the neck associated with the vagus nerve. An 11-year-old girl presented to our hospital with a neck tumor on her right side. Surgical resection was performed, and histopathologic examination demonstrated a high-grade malignant neoplasm. The tumor was composed of sheets of small round proliferating cells, basaloid tumor nests with marked squamous differentiation, biphasic growth pattern with epithelioid tumor nests, and spindle cell proliferation. Immunohistochemically, the tumor cells showed diffuse expression of CD99 and FLI-1. In addition, small round cells and basaloid/squamoid components were immunoreactive for AE1/AE3, CAM5.2, cytokeratin 5/6, high-molecular weight keratin, p63, and p40 (ΔNp63). Reverse transcription polymerase chain reaction and direct sequencing analysis revealed that the tumor harbored a t(11;22) translocation, involving EWSR1 and FLI-1, which are characteristic of EFTs. According to these findings, our case has characteristics of both a subset of adamantinoma-like EFT and EFT with complex epithelial differentiation. We suggest that EFT with complex epithelial differentiation is in a common spectrum with the adamantinoma-like type and that adamantinoma-like EFTs can arise in soft tissue, leading to difficulty in differential diagnosis with malignant epithelial tumors.

Adamantinoma‐like Ewing sarcoma of the parotid gland: Cytopathologic findings and differential diagnosis

“…Interestingly, all the reported cases of AES were characterized by diffuse immunoreactivity for CD 99 and or/FLI‐1 along with detection of the genetic hallmark of EFT ( EWSR1 gene rearrangements) . It is therefore highly recommended to include CD99 and or/FLI‐1 in the IHC panel of the challenging cases of the head and neck with small round blue morphology or when AES is in the differential diagnosis.…”

“…AES has been recently described in the head and neck region including sinonasal tract, parotid gland, thyroid gland and orbit . The presence of epithelioid features which are far different from typical ES/PNET, raise diagnostic challenges in head and neck, which is commonly involved by epithelial and myoepithelial neoplasms with variable morphologic features …”

Round cell sarcomas beyond Ewing: emerging entities

“…All currently reported cases of adamantinoma‐like EFTs have been described within bone and carry an EWSR–FLI1 fusion . Additionally, a unique type of EFT showing complex epithelial differentiation has been reported recently in two separate cases reports, both involving soft tissue and associated with the vagus nerve . This latter EFT subtype is composed of sheets of small blue round cells with interspersed basaloid nests with marked squamous differentiation and spindle cell proliferation.…”

Adamantinoma-Like Ewing Sarcoma Mimicking Basal Cell Adenocarcinoma of the Parotid Gland: A Case Report and Review of the Literature

“…However, cases genotypically and phenotypically compatible with this tumor have also been reported to affect soft tissue and even viscera with or without associated osseous involvement [5,[28][29][30]. Interestingly, two of these cases arose in the soft tissue of the neck affecting the vagus nerve [28,29].…”