The present study was carried out to examine hyaline cells or plasmacytoid cells found in the pleomorphic adenoma of the palate histologically, immunohistochemically, and ultrastructurally. Furthermore, this study presented a review of 13 cases of pleomorphic adenomas with hyaline cells (including our case) in the literature. The round, firm and well-circumscribed tumor, measuring 2×2×2cm, was located in the hard palate of a 28-year old male. Histologically, the tumor consisted mainly of polyhedral or round cells arranged in sheets with the mesenchyma of a fibrous tissue containing hyaline-like component. A relatively large number of hyaline cells with a prominent eccentric nucleus and an eosinophilic cytoplasm were observed among the polyhedral or round cells. The tumor had a small cystic lumen in one area and was almost entirely surrounded with a fibrous capsule. Immunohistochemically, the cytoplasm of the hyaline cell was positive for S-100 protein, vimentin, keratin and GFAP. Ultrastructurally, the cytoplasm was almost filled with intermediate filaments. Clinicopathologically, of 13 previously reported cases of pleomorphic adenomas, 6 were males and 7 females. The ages of the patients ranged from 14 to 46 years with an average of 32.2 years. Of 13 cases, 7 were located in the palatal gland, 5 in the parotid gland and 1 in the submandibular gland.
