DEK::AFF2 fusion-associated papillary nonkeratinizing squamous cell carcinoma of the sinonasal tract and middle ear: a case report and review of the literature

Abstract

Introduction

Nonkeratinizing squamous cell carcinoma (NKSCC) with the DEK::AFF2 fusion is a new entity that was recently added to the 2022 5th edition of the WHO Classification of Tumors of the Head and Neck. This rare malignancy of the sinonasal tract, skull base, and middle ear can be deceptively bland and potentially mistaken as a sinonasal papilloma. We describe a case characterized by multifocal disease, that was initially interpreted as benign.

Materials and Methods

A 22-year-old female with no significant past medical history presented in January 2022 with right-sided nasal congestion and epistaxis. Initial biopsy and subsequent resection resulted in an initial diagnosis of inverted sinonasal papilloma. Three months post-op, the patient returned with continued nasal epistaxis, left-side hearing impairment with otalgia, and left facial weakness. CT scan demonstrated rapid recurrence of the tumor with a new finding of involvement of the middle ear and temporal bone.

Results

Microscopic examination of the recurrence revealed a nonkeratinizing basaloid epithelial process, exhibiting a papillary morphology with acute and chronic inflammation, and necrosis. Lesional epithelium was positive for cytokeratins AE1/AE3, CAM5.2, p63, SMARCB1/INI1 (retained), SMARCA4/BGR1 (retained), but negative for high-risk HPV. PD-L1 combined positive score was 5. Molecular analysis identified a DEK::AFF2 fusion transcript. A diagnosis of DEK::AFF2 fusion-associated papillary NKSCC of the sinonasal tract and middle ear was rendered.

Conclusion

This case exhibited the characteristic bland morphology that commonly leads to a misdiagnosis of a benign process. Immunohistochemical stains and molecular characterization resulted in the final diagnosis of DEK::AFF2 fusion NKSCC, a rare and aggressive neoplasm with potential for locoregional nodal and distant metastasis. Currently, consistent effective therapeutic modalities have not been identified. However, an isolated case report suggested response to treatment with an immune checkpoint inhibitor.