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DEK::AFF2 Fusion-Associated Nonkeratinizing Squamous Cell Carcinoma with Noncontiguous Middle Ear and Sinonasal
Yan Li1, Linxiang Ma2, Wenlin Yang3
1Department of Pathology, Affiliated Hospital of Jining Medical University, Jining, 272029, Shandong, People's Republic of China.
Background:
DEK::AFF2 fusion-associated nonkeratinizing squamous cell carcinoma is a recently recognized HPV-independent entity characterized by deceptively bland morphology and potential mimicry of benign or inflammatory lesions.
Case Presentation:
A 21-year-old woman presented with recurrent left-sided otorrhea and progressive hearing loss. Imaging demonstrated noncontiguous lesions involving the left middle ear/mastoid compartment and the sinonasal region. Histologically, both lesions showed nonkeratinizing squamous proliferation with focal papillary/inverted architecture, mild to moderate cytologic atypia, and focal stromal invasion. Immunohistochemically, the tumor exhibited diffuse nuclear AFF2 expression, positivity for CK5/6 and p40, wild-type p53 expression, and negative p16 and INSM1. Targeted next-generation sequencing confirmed DEK::AFF2 fusion in both lesions.
Conclusion:
This case expands the anatomic spectrum of DEK::AFF2 fusion-associated nonkeratinizing squamous cell carcinoma by demonstrating noncontiguous middle ear and sinonasal involvement. Recognition of its characteristic morphologic, immunophenotypic, and molecular features is essential to avoid misdiagnosis.
