The mucocele is the most common inflammatory lesion of the salivay glands and results from either blockage or rupture of a salivary gland duct, with consequent leakage of saliva into the surrounding connective tissue stroma. Mucocele occurs most often in toddlers, young adults, and older adults, and typically manifests as a fluctuant swelling of the lower lip that may change in size, particularly in association with meals (
Fig. 15.5A ). Histologic examination demonstrates a cystlike space lined by granulation tissue or fibrous connective tissue that is filled with mucin and inflammatory cells, particularly macrophages (
Fig. 15.5B ). Complete excision of the cyst and the minor salivary gland constitutes definitive treatment.
Bacterial sialadenitis is a common infection that most often involves the major salivary glands, particularly the submandibular glands. The most frequent pathogens are Staphylococcus aureus and Streptococcus viridans. Duct obstruction by stones (sialolithiasis) is a common antecedent to infection; it may also be induced by impacted food debris or by edema consequent to injury. Dehydration and decreased secretory function can also predispose to bacterial invasion. Systemic dehydration, with decreased salivary secretions, may predispose to suppurative bacterial parotitis in older adult patients following major thoracic or abdominal surgery. Such obstruction and bacterial invasion lead to nonspecific inflammation of the affected glands that may be largely interstitial or, when induced by staphylococci or other pyogens, may be associated with suppurative necrosis and abscess formation.
Autoimmune sialadenitis, better known as Sjögren syndrome, is discussed in Chapter 5.
Despite their relatively simple morphology, the salivary glands give rise to at least 30 histologically distinct tumors (
Table 15.1 ). A small number of these neoplasms account for more than 90% of tumors. Overall, salivary gland tumors are relatively uncommon and represent less than 2% of all human tumors. Approximately 65% to 80% arise within the parotid, 10% in the submandibular gland, and the remainder in the minor salivary glands, including the sublingual glands. Approximately 15% to 30% of tumors in the parotid glands are malignant. By contrast, approximately 40% of submandibular, 50% of minor salivary gland, and 70% to 90% of sublingual tumors are cancerous. Thus, the likelihood that a salivary gland tumor is malignant is inversely proportional, roughly, to the size of the gland.
Fig. 15.5 Mucocele.(A)Fluctuantfluid-filledlesiononthelowerlipsubse-quenttotrauma.(B)Cystlikecavity(right) filledwithmucinousmaterialandlinedbyorganizinggranulationtissue.Thenormalglandaciniareseenontheleft.
Salivary gland tumors usually occur in adults, with a slight female predominance, but about 5% occur in
Table 15.1 Histopathologic Classification and Prevalence of the Most Common Benign and Malignant Salivary Gland Tumors
NOS, Nototherwisespecified.DatafromEllisGL,AuclairPL,GneppDR:Surgical pathology of the salivary glands, Vol 25: Major problems in pathology. Philadelphia,1991,Saunders.