Adamantinoma-like Ewing Sarcoma of the Nasal Cavity: A Rare Clinical Presentation with Deceptive Histopathologic Features

Abstract

Ewing sarcoma (ES) is a malignant round cell tumour (MRCT) that usually involves bone and soft tissue of young and paediatric populations. ES of the head and neck region is uncommon. Adamantinoma-like Ewing sarcoma (ALES) is a rare variant of ES that shows complex epithelial differentiation on histopathology and immunohistochemistry (IHC). It demonstrates a t(11;22) translocation and EWSR1-FLI1 fusion. Most documented cases of ALES of the head and neck region were initially misdiagnosed as epithelial tumours. We present a rare case of ALES of the nasal cavity in a young female. The patient subsequently underwent chemotherapy and showed an excellent response. Awareness of this entity is important for pathologists and oncologists due to its distinct therapeutic and prognostic implications. We propose performing upfront NKX2.2 and CD99 IHC studies, as well as other lineage specific IHC markers, in any poorly differentiated MRCT of head and neck region.

Adamantinoma-like Ewing Sarcoma (ALES) May Harbor FUS Rearrangements

“…5 All ALES reported to date have been shown to harbor EWSR1 rearrangements with presumed fusion FLI1. 3,4,[6][7][8][9] Rare cases of Ewing sarcoma have been reported to demonstrate alternative translocations involving FUS, however, this has never been previously reported to occur in ALES. [10][11][12][13] Here, we describe 6 cases of EWSR1-negative ALES with FUS rearrangements including a case with FUS:: FLI1, which has not been previously reported in the Ewing family of tumors.…”

“…All ALES reported to date have been shown to harbor EWSR1 rearrangements with presumed fusion FLI1. 3,4,6–9 Rare cases of Ewing sarcoma have been reported to demonstrate alternative translocations involving FUS , however, this has never been previously reported to occur in ALES 10–13 …”