DEK::AFF2 Squamous Cell Carcinomas of the Sinonasal Region and Temporal Bone Diagnosed After Recurrences: A Report of Two Patients.

DEK::AFF2 squamous cell carcinoma is a recently recognized entity characterized by a non-viral-related non-keratinizing squamous cell carcinoma with chromosomal rearrangement between DEK on 6p22.3 and AFF2 on Xq28. This neoplasm is associated with an aggressive clinical behavior, particularly regarding local recurrences and distant metastases even with its deceptively bland histomorphology. In this article, we report on 2 patients with DEK::AFF2 squamous cell carcinomas, which were only diagnosed at the time of recurrence. Patient #1 was originally misdiagnosed with inverted papilloma. This occurred 3 years previously, and at second presentation the tumor was recurrent in the nasal cavity and paranasal sinuses. Patient #2 was identified at second recurrence of a "nasopharyngeal carcinoma," initially diagnosed in the nasopharynx 5 years earlier, with a subsequent recurrence in the middle ear 2 years later, involving the mastoid process. The immunophenotypic and molecular work-up, as well as the management of these patients, are discussed. In our review of the English-language literature on DEK::AFF2 squamous cell carcinomas, we identified 41 patients, including our 2 patients. Of these, 26 had information on their clinical course. Sixty-nine percent of patients reported a history of locoregional recurrence, and 19% reported a history of distant metastases, with an average follow-up duration of 36 months after multimodality therapies. Given our improved understanding of DEK::AFF2 squamous cell carcinoma as an aggressive tumor, it is crucial to differentiate this neoplasm from other potential histomorphologic mimickers to ensure early and accurate diagnosis.