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

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.