Fig. 4

Histopathologic, immunohistochemical and molecular pathology findings of sinonasal tract and skull base SCC and DEK::AFF2 carcinomas. Keratinizing SCCs with intercellular bridges and obvious keratin pearl formation (A-B), and high expression levels of Ki-67 (C); DEK::AFF2 carcinomas demonstrated a mix of exophytic and endophytic growth, with broad papillary fronds (D), immature transitional-type epithelial cells monotonous and round to oval with delicate chromatin and prominent nucleoli (E), a blunted papillae and pushing pattern of invasion into stroma as interconnecting ribbons (F); a dense population of tumor-infiltrating neutrophils (G); Ki-67 index was approximately 5% (H), The DEK gene rearrangement was confirmed by FISH (I)