Salivary duct carcinoma.

Abstract

Salivary duct carcinoma (SDC) is a distinctive salivary gland neoplasm morphologically characterized by intraductal and infiltrating components. Most tumors occur in the major salivary glands and demonstrate a propensity for invasive growth with early regional and distant metastases. Therefore, SDC is regarded as a high-grade malignancy in the current classification of salivary gland neoplasms. In an effort to identify clinically relevant prognostic features, we studied the clinicopathologic and immunohistochemical findings in 15 SDC, with ultrastructural evaluation of three tumors. Thirteen SDC occurred in the parotid gland, one in the Stensens duct, and one in the palate. Twelve patients were men (ratio of men to women = 4:1). Patients ranged in age from 39 to 81 years (mean = 59 years). Tumor size varied from 1.2 to 6.5 cm (mean = 3.1 cm). An intraductal component was identified in 10 of 14 primary SDC that made up 10% to 95% of the tumor. In three SDC a preexisting pleomorphic adenoma was identified. Immunohistochemical and electron microscopic evaluation showed the SDC to be composed entirely of ductal cells, and one tumor exhibited features of striated duct differentiation. SDC show a broader clinicopathologic spectrum than previously described. The tumor may arise in a pleomorphic adenoma. The proportion of intraductal and extraductal growth is variable and of prognostic significance. Although the majority of SDC behave in a high-grade fashion, those with a predominant intraductal component of greater than 90% (PID-SDC) and minimally invasive (< 8 mm) SDC in pleomorphic adenoma appear to have a more favorable prognosis.