Ultrastructure of a sialadenoma papilliferum

A case of sialadenoma papilliferum occurring in the hard palate of a 56-year-old Japanese man is presented. A pedunculated, nonencapsulated and small mass consisted of predominantly exophytic proliferation of a double- or multi-layered duct epithelium with a concomitant overgrowth of squamous epithelium. This characteristic papillary lesion was demonstrated by electron microscopic examination to be mainly composed of salivary gland duct epithelium intermingled with a few of myoepithelial cells. Moreover, these duct cells were interpreted ultrastructurally as an intercalated duct cell. This finding indicates that sialadenoma papilliferum may be an intercalated duct cell in origin.