Fig. 2

The main histomorphological features of the tumor. a The tumor was composed of polyhedral neoplastic cells with intercellular bridges and some degree of nuclear pleomorphism (hematoxylin and eosin [H&E]; original magnification × 40). b Homogeneous eosinophilic acellular material between neoplastic proliferations that stained positive for Congo red (Congo red stain; original magnification × 40). c Intercellular deposits with apple-green birefringence on polarized light examination of the Congo red stained sample (original magnification × 40). d Tumor areas with nuclear pleomorphism (H&E; original magnification × 40). e Tumor areas with nuclear pleomorphism and multinucleate giant cells (H&E; original magnification × 40). f Scattered S100 positive clear cells between polyhedral neoplastic cells (immunostaining, original magnification × 20). g Tumor comprises areas with cementum-like material (*) (H&E; original magnification × 10). h Tumor invasion of the maxillary sinus mucosa without involvement of the lining epithelium (H&E; original magnification × 10). i Tumor invasion of vestibular mucosa without involvement of the lining epithelium (H&E; original magnification × 10)