Primary squamous cell carcinoma of the parotid gland: a case report with electron microscopic findings.

Primary squamous cell carcinoma of the parotid gland is a rare tumor. Histological and ultrastructural features of a primary squamous cell carcinoma arising in the right parotid gland is presented. Light microscopically the tumor consisted of poorly differentiated squamous cell nests. PAS reaction was negative. Ultrastructurally the tumor cells were oval or spindle shaped and the cytoplasmic processes were frequently found. The majority of the tumor cells contained numerous intermediate filaments in their cytoplasm. No secretory granule was found. The desmosomes were well developed. It is known that mucoepidermoid carcinoma may be often misdiagnosed as squamous cell carcinoma. These findings can enable us to distinguish primary squamous cell carcinoma from mucoepidermoid carcinoma of the parotid gland.