Lipoadenoma of the parotid gland with probable striated duct differentiation.

We report an example of lipoadenoma of the parotid gland, a previously undescribed tumor of the salivary gland. It is a well-circumscribed tumor comprising an intimate admixture of mature fat cells and branching narrow tubules. The tubules were elongated and had small or absent lumina, resulting in a remarkable Sertoliform pattern. They were lined by columnar cells, which were supported by a basal cell layer. The latter cells lacked evidence of myoepithelial differentiation but were best highlighted by immunostaining for high molecular-weight cytokeratin (34 beta E12). Comparison with the normal salivary gland components showed the greatest homology of the neoplastic tubules with the striated duct, which normally has an incomplete basal cell layer. The latter phenomenon is under-recognized, with some current textbooks still describing the presence of a single cell type only in the striated duct of the salivary gland.