Salivary Gland FNA: Anatomic, Clinical, and Technical Considerations

The major salivary glands consist of the parotid, the submandibular, and the sublingual glands. Under the control of the parasympathetic nervous system, the major salivary glands are responsible for the principal portion of saliva produced, which can be as much as 1.5 liters per day. The minor salivary glands of the oral cavity, pharynx, and upper airways contribute only a small percentage of the overall volume of saliva, but they are particularly important for supplying the mucus layer that protects the tissues of the oral cavity and upper respiratory tract. Embryologically, the major salivary glands develop during the 6th to 8th weeks of gestation. The parotid gland arises first from ingrowth of the oral ectoderm into the surrounding mesenchyme. By the 7th week of development, the parotid gland moves in a dorsal and lateral direction to reside in the preauricular region, and by the 10th week, the facial nerve divides the surrounding parotid gland into anatomic superficial and deep compartments. A majority of parotid gland tumors develop within the superficial lobe, making FNA and clinical management relatively easy. Tumors originating within the deep lobe of the parotid gland usually present as pharyngeal swellings due to expansion into the parapharyngeal space. The parotid gland is unique among the salivary glands in that it incorporates lymphoid tissue during development, sometimes with entrapment of salivary gland epithelial cells. The latter are believed to be the source of lesions such as Warthin tumor and lymphoepithelial cysts. The minor