Xanthogranulomatous epithelial tumour of the calcaneus in a 32-year-old female: a rare entity.

Xanthogranulomatous epithelial tumour (XGET) is a recently described, rare mesenchymal neoplasm characterized by a HMGA2::NCOR2 gene fusion. We report a case of primary intraosseous XGET in the calcaneus of a 32-year-old female presenting with a 10-month history of heel pain. Initial differential diagnosis based on imaging features of the lytic calcaneal lesion included giant cell tumour of bone (GCTB) and solid aneurysmal bone cyst (sABC). Histopathology revealed a bland appearing lesion with xanthomatous histiocytes and giant cells, but immunohistochemistry showed diffuse cytokeratin positivity. Definitive diagnosis was established via molecular confirmation of the HMGA2::NCOR2 fusion and absence of H3F3A and USP6 alterations. This case documents the radiological features of a rare entity that mimics common bone tumours and emphasizes the role of molecular pathology in distinguishing XGET from other more frequent giant cell-rich lesions.