12 Inflammatory Salivary Gland Disorders
• Dome-shaped, bluish, sessile nodules, mucoceles are commonly located on the lower labial mucosa (70% to 90%), ventral tongue (ranula), buccal mucosa, and floor of mouth; they wax and wane and are usually painless (Fig. 12-1, A-C); 44% of mucoceles resolve spontaneously.
• Superficial mucoceles are seen in patients with hyposalivation; they are most frequent on the palate (such as in patients with chronic graft-versus-host disease) and resemble painless blisters or vesicles, often leading to a clinical misdiagnosis of herpes infection (see Fig. 12-1, D); the latter are almost always extremely painful.
Mucoceles are pseudocysts that arise from trauma to the excretory salivary duct; this leads to escape of mucous into the surrounding soft tissues, which become walled off by granulation tissue and eventually organized by fibrous tissue.
• Cystlike cavity fills with mucin with variable numbers of neutrophils, muciphages, and, sometimes, eosinophilic spherules surrounded by condensed granulation tissue containing muciphages; these globules are mucicarmine positive and may represent mucin condensations; a feeder duct exhibiting squamous metaplasia may be seen; mucin may be inconspicuous within the wall (Figs. 12-2 and 12-3).
• Mucin may be present diffusely in the connective tissue (Fig. 12-4); lesions not removed intact manifest as fragments of granulation tissue with muciphages (Fig. 12-5); ventral tongue lesions tend not to have a thick wall of granulation tissue (Fig. 12-6).
• Minor salivary glands exhibit variable degrees of obstructive changes, namely acinar atrophy, ductal dilatation with inspissated secretions, periductal hyalinization, interstitial fibrosis, and interstitial lymphoplasmacytic infiltrate (Fig. 12-7).
• Organizing mucoceles consist of a solid mass of granulation tissue with muciphages; mucin generally is inconspicuous, and a mucin pool is absent (Fig. 12-8); muciphages may sometimes have clear cytoplasm (Fig. 12-9).
FIGURE 12-2 Mucocele. A, Pool of mucin containing eosinophilic globules surrounded by granulation tissue; part of feeder duct present. B, Surrounding granulation tissue contains eosinophilic globules. C, Hyaline spherules (myxoglobulosis) within mucin. D, Eosinophilic globules in connective tissue stain for mucicarmine (inset).
• An organizing mucocele with a predominance of clear cells may resemble salivary gland neoplasm such as mucoepidermoid carcinoma or even clear cell carcinoma, but there is lack of stromal invasion by nests of neoplastic cells.
• Obstructive changes are often diffuse and should not be confused with autoimmune sialadenitis seen in Sjögren syndrome, in which obstructive changes are minimal and the lymphocytic infiltrate is strikingly periductal, at least in early stages (see later); focal periductal lymphocytic infiltrates are not uncommon in obstructive sialadenitis.
Chi AC, Haigney RJ2nd, Spagnoli DB, et al. Papillary synovial metaplasia-like change in oral mucoceles: a rare and previously undescribed histopathologic variant of a common oral lesion. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2010;109:268-273.
Salivary Duct Cyst (Salivary Retention Cyst, Sialocyst)
• These cysts consist of cystically dilated excretory salivary duct that may be lined by a double layer of low cuboidal-to-columnar cells or may exhibit metaplastic change—squamous, ciliated cell, or oncocytic (oncocytic sialocyst); it may have slight papillary projections in the lining (Figs. 12-13 to 12-15); a sialolith may be present; variable lymphoplasmacytic infiltrate present.
• Oncocytic sialocystosis (papillary or otherwise) shows multiple cystic structures in both extralobular and intralobular locations; surrounding minor glands exhibit obstructive changes (see Mucocele) (Figs. 12-16 and 12-17); should not be overdiagnosed as papillary cystadenoma.
FIGURE 12-16 Oncocytic sialocystosis. A, Extralobular and intralobular dilated ducts with marked sclerosing sialadenitis in surrounding glands. B, Ducts lined by uniformly thin epithelium. C, Lining is composed of pseudostratifed columnar, ciliated, and mucous cells.