Fig. 2

Endoscopic view of the left nasal cavity before sinus surgery (A) and directly afterward (B), and histopathological examination of the polyp removed from the left sphenoid sinus (C). The middle nasal concha (A, asterisk) and the orbital plate of the ethmoid bone (lamina papyracea; A, cross) surround the ethmoid sinus complex. Recurrent nasal polyps (A, NP) are congesting the nasal cavity and extending up to and within the left sphenoid sinus and the adjacent Onodi cell more posteriorly. During surgery, the remaining bony septa that had enclosed the left optic nerve were removed (B, double asterisk) and the sphenoid sinus and adjacent Onodi cell (B, arrow) were widely opened. Histopathological analysis of the polyp from the sphenoid sinus (C; hematoxylin–eosin staining), which had been in direct contact with the optic nerve, revealed thickened basement membranes (panel C, BM) and increased tissue eosinophilia (C, arrowheads), suggesting a type 2 inflammatory endotype