Extraosseous Ewing Sarcoma of the Oral Cavity: 14‐Year Follow‐Up of a Case With Distinct Clinical Features

ABSTRACT Objective Ewing sarcoma is a highly aggressive malignant tumour that most often arises in bone but can also occur in soft tissues. Primary involvement of the head and neck region is particularly rare, especially regarding its extraosseous presentation. In this report, we present the clinicopathological, immunohistochemical and molecular findings of an extraosseous Ewing sarcoma in a 41‐year‐old male who presented with a painless swelling on the left side of the face. Materials and Methods Clinical examination revealed a firm, nodular mass extending from the left buccal mucosa to the posterior retromolar region. An incisional biopsy was performed, and histopathological analysis showed small round cells with round nuclei, fine chromatin and poorly defined clusters of neoplastic cells within fibrous connective tissue. Immunohistochemical staining demonstrated strong membranous positivity for CD99, diffuse cytoplasmic expression of vimentin and moderate positivity for neuron‐specific enolase (NSE). There was also slight positivity for AE1/AE3 cytokeratin and chromogranin, while epithelial membrane antigen (EMA) and leukocyte common antigen (LCA) were negative. Results The diagnosis of extraosseous Ewing sarcoma was confirmed by fluorescent in situ hybridization (FISH). The patient received multi‐agent chemotherapy for 1 year, combined with radiotherapy. After 14 years of follow‐up, no signs of recurrence or metastasis were observed. Conclusion The mentioned findings underscore the importance of a thorough histopathological, immunohistochemical and molecular approach for the accurate diagnosis of Ewing sarcoma and the management of such rare cases.