Small Round Cells, Big Diagnostic Challenge: Ewing Sarcoma of the Mandible in a Child

Abstract

Ewing sarcoma is a malignant small round blue cell tumour which is aggressive in nature and is driven by recurrent chromosomal translocations involving FET–ETS family genes, most frequently the EWSR1–FLI1 fusion. It primarily affects children and adolescents, commonly arises in the diaphysis of long bones. Occurrence in the head and neck region is uncommon, and primary involvement of the mandible is particularly rare.Here we describe the case of a 15-year-old boy who presented with a gradually enlarging painful swelling over the right cheek. On Fine-needle aspiration cytology features were of small round blue cell tumour with occasional rosette-like arrangements. The diagnosis of Ewing sarcoma of the mandible was subsequently established by histopathological examination and immunohistochemistry, which demonstrated diffuse positivity for CD99, NKX2.2, and FLI1.This case underscores the importance of correlating clinical presentation with radiological, cytological, histopathological, and immunohistochemical findings to achieve an accurate diagnosis of this uncommon tumour and facilitate timely management.