DEK::AFF2-Associated Papillary Squamous Cell Carcinoma of the Sinonasal Tract: Clinicopathologic Characterization of 9 Cases.

Abstract

Introduction: DEK::AFF2 fusion-associated carcinoma, a recently recognized entity predominantly localized to the sinonasal tract and skull base, remains diagnostically challenging due to its poorly defined clinicopathological spectrum and epidemiological profile. Despite its deceptively bland histomorphology, this neoplasm is paradoxically linked to aggressive clinical behavior and elevated mortality rates.

Purpose: To delineate the clinicopathological and molecular characteristics of DEK::AFF2 fusion-associated carcinomas to elucidate their biological drivers and refine therapeutic strategies.

Methods: A retrospective cohort study was conducted on some cases initially diagnosed as sinonasal papilloma of various types, with or without dysplasia or associated malignant transformation. DEK::AFF2 fusion was confirmed by DEK break-apart fluorescence in situ hybridization (FISH). Molecular features were assessed using immunohistochemistry (IHC) and in situ hybridization (ISH) to differential diagnosis. Clinical outcomes were analyzed for recurrence and disease-specific mortality.

Results: Nine cases with DEK gene rearrangements were identified. The cohort comprised patients aged 51-76 years (median: 59 years), with a male predominance (M:F = 7:2). All cases demonstrated nuclear positivity for p40/p63 and AFF2 (30% ~90% tumor cells), while staining for p16 and Epstein-Barr encoded mRNA (EBER) was uniformly negative by IHC and ISH. Ki-67 index ranges from 5 to 40% with the median at 20%. Local recurrences occurred in 55.6% (5/9) of patients within 10-30 months following initial therapeutic intervention. The disease-specific mortality observed in 22.2% (2/9) of cases.

Conclusion: DEK::AFF2 fusion-associated carcinoma is characterized by a clinicopathological dichotomy: bland histological features contrast with aggressive biological behavior and poor prognosis in the nasal cavity, paranasal sinuses, and skull base.