There are three major and innumerable minor pairs of salivary glands. The largest, on the cheek, is the parotid, where most neoplasms arise. The smaller major glands are the sublingual and submandibular , under the tongue and jaw. In general, the smaller the gland, the higher the proportion of its neoplasms that are malignant. Salivary neoplasms can arise in virtually any part of the sinonasopharyngeal system .

The first major cell type is the secretory cell . The salivary glands are composed of serous and mucinous secretory units and ducts (Figure 25.1). Serous cells are wedge-shaped (like pie slices) and arranged in acini around ducts. They are full of blue to purple granules. Mucinous cells have basal nuclei and apical mucin, like goblet cells; these are also arranged in acinar formations. The parotid is primarily serous, the submandibular is mixed, and the sublingual is primarily mucinous.

The second major cell type is the duct cell . The duct system has three types of ducts: the terminal or intercalated ducts, the intermediate-sized striated ducts, and the interlobular large ducts . Each has a different epithelium and is theoretically associated with different tumor types. The intercalated ducts are small profiles with low cuboidal epithelium, similar to a bile ductule (Figure 25.2). Striated ducts are more proximal and are larger, with pink columnar cells full of mitochondria and striated basal borders (hard to see). Interlobular or excretory ducts have pseudostratified columnar epithelium with or without goblet and squamous metaplasia. Different tumors have some morphologic similarity to these different ducts, which may help you keep the neoplasms straight.

The third major cell type is the myoepithelial cell . These cells, as in breast, surround acini and ducts. They are normally pale stellate cells with small nuclei and are very hard to identify in normal salivary gland. However, many neoplasms arise from the epithelial–myoepithelial cell line or, more specifically, from cells that can differentiate into either line. This creates a diagnostic nightmare, because the myoepithelial cells alone can take four different forms: spindled, plasmacytoid, epithelioid, and clear. Therefore, you must recognize any of these variants as myoepithelial (their immunologic profiles change with their form, unfortunately) and lump some very different-looking tumors into the same basket. Table 25.1 lists the most common neoplasms.