Ewing sarcoma of maxilla masquerading as odontogenic lesion; And role of NKX2.2 for confirmatory diagnosis: A rare case report

Ewing sarcoma (ES), defined as a malignant small round blue cell neoplasm of bone and soft tissue occurs most frequently in children and young adults. ES is an aggressive tumor showing rapid growth and metastasis. It has been documented to strike the skull, supraclavicular region, parotid region, orbital floor, nasal cavity, maxilla, mandible, and zygoma in the head and neck region. The incidence of ES as a primary lesion in the head and neck region is reportedly 2%–3% of all cases only. The differential diagnoses for these tumors include alveolar rhabdomyosarcoma, desmoplastic small round cell tumor, poorly differentiated round cell synovial sarcoma, small cell osteosarcoma, and mesenchymal chondrosarcoma. Here we report a case of primary Ewing sarcoma involving the maxilla in a 12 year male with its clinical, radiological, histopathological findings, initially misdiagnosed as a benign entity. Special emphasis on hallmark immunohistochemical features are also discussed. • Rare Tumour Presentation • Diagnostic Challenge • Role of IHC Marker NKX2.2