Immunohistochemical study on sebaceous adenoma and sebaceous carcinoma arising in parotid gland.

The present study presents two cases of parotid mass diagnosed as sebaceous adenoma and sebaceous carcinoma in which immunohistochemical staining was performed for cytokeratins, vimentin, S-100 proteins, lactoferrin, lysozyme, alpha 1-antichymotrypsin, alpha 1-antitrypsin, and proliferating cell nuclear antigen to evaluate the characteristics of tumor cells and to distinguish these lesions from their counterparts in the skin. Sebaceous adenoma had circumscribed lobules containing sebaceous cell nests with well differentiated sebaceous cells surrounded by basaloid cells and a population of transitional cells. Sebaceous carcinoma had cellular pleomorphism and nuclear atypia and a population of cells resembling neoplastic myoepithelial cells of pleomorphic adenoma. The profile of markers used in the present study when compared with studies on sebaceous tumors of skin and the characteristics of other salivary neoplasms reasonably allowed us to conclude that the sebaceous differentiation and sebaceous tumors in salivary glands may differ from that of their counterparts in skin. The histogenesis of salivary sebaceous neoplasms may be attributable to the process of sebaceous metaplasia in the salivary tissues and based on our finding of similar immunohistochemical profile of sebaceous cells in sebaceous carcinoma with that of neoplastic myoepithelial cells in pleomorphic adenoma as reported earlier, sebaceous neoplasms may have a common histogenetic origin with other salivary neoplasms. However, their origin from the sebaceous glands normally present in the salivary tissues could not be excluded.