Oral Undifferentiated Pleomorphic Sarcoma: A Novel Gene Fusion and a Comprehensive Literature Review.

Undifferentiated pleomorphic sarcoma (UPS) is a rare, high-grade soft-tissue sarcoma characterized by a patternless proliferation of bizarre pleomorphic tumor cells lacking identifiable lineage differentiation. Its occurrence in the oral cavity is exceptionally uncommon and poses significant diagnostic challenges due to its morphological overlap with a wide spectrum of other malignancies. : We report a novel case of oral UPS in a 54-year-old woman, characterized by an exceptionally large size and a rapidly progressive clinical course. The diagnostic evaluation included clinical, radiological, histopathological, immunohistochemical, and molecular analyses conducted within a multidisciplinary framework. A comprehensive review of the literature on oral UPS was also performed. : The patient underwent an aggressive demolitive surgical approach due to the extent of the lesion. Molecular analysis revealed a previously unreported gene fusion. The literature review highlighted the rarity of oral UPS, its geographic predilection for Central and East Asia, possible associations with traumatic events, and its heterogeneous clinical and histopathological presentations. : This case underscores the critical importance of a thorough diagnostic workup to ensure the accurate diagnosis and appropriate management of this rare and aggressive tumor. Multidisciplinary evaluation is essential, especially in anatomically complex and diagnostically challenging presentations such as oral UPS.