Fig. 3

Histopathologic, immunohistochemical and molecular pathology findings of sinonasal tract and skull base hyalinizing clear cell carcinoma (HCCC). Note the cords and trabeculae growth patterns with prominent hyalinized collagen (A), proportions nests and cords of bland cells with clear cytoplasm with occasional gland-like formation or mucin production (arrows) (B), papillary structure of the fibrovascular axis (C), predominant clear cells, eosinophilic cells and their mixture in various proportions (arrows) (D), HCCC exhibited surface epithelial involvement (E), varying degrees of necrosis (green arrows) and nerve invasion (yellow arrows) (F), neoplastic cells strongly and diffusely expressed CK7 (left) and p63 (right) (G), p16 positive (left) and two cases showed relatively high Ki-67 (right) (H), FISH revealed EWSR1-ATF1 fusion in all HCCC cases (I). (× 1000)