FGFR3::TACC3 Fusion and NOTCH1 Loss-of-Function in a Case of HPV-Associated Sinonasal Squamous Cell Carcinoma: Diagnostic Challenge and Implications for Targeted Therapy.

Sinonasal squamous cell carcinoma (SNSCC) comprises a heterogeneous group of tumors with emerging molecular subtypes. Human papillomavirus (HPV)-associated SNSCC is a distinct entity, although actionable genomic alterations beyond HPV-driven pathways remain underexplored. Distinguishing HPV-associated SNSCC from carcinoma ex inverted papilloma can be particularly challenging in limited biopsy specimens, as these lesions may appear morphologically similar. We report a case of HPV-associated SNSCC with concurrent FGFR3::TACC3 fusion and NOTCH1 p.C1416 stop-gain mutation.