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

<italic>DEK::AFF2</italic> squamous cell carcinoma is a recently recognized entity characterized by a non-viral-related non-keratinizing squamous cell carcinoma with chromosomal rearrangement between <italic>DEK</italic> on 6p22.3 and <italic>AFF2</italic> 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 <italic>DEK</italic>::<italic>AFF2</italic> 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 <italic>DEK</italic>::<italic>AFF2</italic> 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 <italic>DEK</italic>::<italic>AFF2</italic> 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. [ABSTRACT FROM AUTHOR]