Primary squamous cell carcinoma of accessory parotid gland duct epithelium: report of a case.

A rare case of primary squamous cell carcinoma surrounding Stensen's duct in a 75-year-old man is presented. The tumor was a relatively well-defined, hard, subcutaneous mass, measuring 18 x 14 x 9 mm and situated in the right cheek. Microscopic examination of an excisional biopsy specimen revealed tumor cells showing squamous differentiation, a papillary growth pattern, and ductal structures with comedo necrosis. Immunohistochemical studies showed positive reactivity for KL-1 (cytokeratin, monoclonal), epithelial membrane antigen, and carcinoembryonic antigen in some tumor cells. The origin of the tumor was thought to be the accessory parotid gland duct epithelium.