An elderly Filipino female presented with a 5-year enlarging left nasolacrimal mass initially diagnosed as Inverted Papilloma of the Lacrimal Sac. Repeat biopsy revealed a papillomatous neoplasm with thick and thin papillae, solid invaginating lobules, and anastomosing trabeculae of monomorphic squamotransitional cells, briskly infiltrated by neutrophils. Mucocytes, respiratory epithelium, and microcysts, typical of Inverting Sinonasal Papilloma, are absent. Immunohistochemistry, including a validated AFF2 IHC, confirmed the diagnosis of DEK::AFF2 sinonasal carcinoma. Awareness of this emerging entity is essential to prevent misdiagnosis and prompt surgical management.