METHODS
His laboratory findings were unremarkable. A non-contrast-enhanced computerized tomography followed by contrast-enhanced computed tomography scan of the paranasal sinus revealed an ill-defined soft tissue density lesion measuring 3.2x2.6x2.1cm in the right posterior ethmoid sinus extending up to the right frontal sinus and nasal cavity causing erosion of adjacent bones involving right fovea ethmoidalis, lateral lamella, vertical lamella and middle turbinate with an indistinct floor of right olfactory groove. Minimal mucosal thickening is noted in the right maxillary sinus. No definite intracranial or intraorbital extension was noted.
A preliminary diagnosis of right-sided sinonasal mass was made and the patient underwent endoscopic sinus surgery. Intraoperative findings include a friable mass occupying the ethmoid and frontal sinus and extending up to the nasal cavity and lamina papyracea dehiscence was also noted. The resected mass was then sent for histopathological examination. The patient was discharged on the first postoperative day with no complaints.
Histopathological examination revealed atypical cells arranged in papillary patterns, sheets, and clusters infiltrating into the fibrotic stroma. These atypical cells are basaloid and exhibit pleomorphism. Individual cells have a high nucleo-cytoplasmic ratio, hyperchromatic nuclei, few visible nucleoli, and a scant amount of cytoplasm.(Figure 1) Mitosis and areas of necrosis were seen. Tumor tissue was subjected to further immunohistochemistry (IHC) analysis showed tumor cells positive for CK5/6, EBV, CK, and P40 and negative for S-100. (Figure2a-2d) INI showed loss of expression.(Figure 3) Based on the overall histomorphological features combined with the immunohistochemical profile, a final diagnosis of SMARCB1-deficient sinonasal carcinoma was made.