Intraoral Salivary Duct Cyst: Clinical and Histopathologic Features of 177 Cases

Abstract

The salivary duct cyst (SDC) is a reactive ductal ectasia most frequently seen in major salivary glands, and likely caused by obstruction. The aim of this study is to define the clinical and histopathologic spectrum of intraoral SDCs. Cases were retrieved from the archives of Harvard School of Dental Medicine/StrataDx, Inc. from January 2012 to August 2014. There were 177 cases of which 103 (58.2%) occurred in females, with a median age of 56 (range 2-95). Approximately half of cases (45.8%) presented in the area of the buccal mucosa, lower lip mucosa, or mandibular vestibule, and 23.2% presented in the floor of mouth. SDCs were lined at least focally by 1-2 layers of cuboidal/columnar epithelium in 85.3% of cases and showed varying degrees of metaplasia (oncocytic, mucous cell, squamous, ciliated, apocrine-like) in 68.4% of cases. Intraluminal mucous stasis was present in 41.8% of SDCs, incipient calcification was present within 4.5% of SDCs, and chronic obstructive sialadenitis was seen in 90.2% of cases. No cysts showed adenomatous ductal proliferations or true papillary structures with fibrovascular cores, although 41.2% exhibited reactive undulation of cyst lining. Thirty-nine 'papillary oncocytic cystadenoma-like' SDCs (22.0%) demonstrated complete oncocytic metaplasia and marked undulation. An additional seven such cysts (4.0%) had a 'Warthin tumor-like' lymphoplasmacytic infiltrate. Intraoral SDCs occur most commonly in the sixth decade of life in locations distinct from extravasation mucoceles, likely secondary to intraluminal obstruction. SDCs show diverse histopathology and certain phenotypic variants may be mistaken for papillary oncocytic cystadenoma or Warthin tumor.

Keywords: Cystadenoma; Mucocele; Mucous retention cyst; Salivary duct cyst; Sialocyst; Warthin tumor.

Fig. 1

Mucosal-colored, mildly translucent SDC of left sublingual caruncle

Fig. 2

a Typical SDC with cystically dilated excretory duct, uninvolved excretory duct (arrow) is noted bottom right (×40). b SDC involving excretory duct as well as multiple smaller intralobular ducts located within distinct minor salivary gland lobules (×40). c SDC with intraluminal mucous plug (×40). d Early calcification occurring within longstanding SDC (×100)

Fig. 3

a SDC (top, arrow) lined by 1–2 layers of low cuboidal/columnar epithelium and juxtaposed to normal excretory duct epithelium (bottom) consisting of columnar luminal and cuboidal abluminal cells (×400). b Cyst lining exhibiting oncocytic metaplasia (×400). c Cyst lining exhibiting mucous cell metaplasia (×400). d Cyst lining exhibiting squamous metaplasia (×400). e Cyst lining exhibiting ciliated cell metaplasia (×400). f Cyst lining exhibiting apocrine-like metaplasia (×400)

Fig. 4

a Inflamed SDC exhibiting metaplastic changes and moderate chronic inflammation with germinal center formation (arrow) (×200). b Minor salivary gland lobule proximal to SDC exhibiting severe chronic obstructive sialadenitis (×20). c Chronic obstructive sialadenitis characterized by acinar atrophy, ductal dilatation, interstitial fibrosis, and interstitial chronic inflammation (×100). d Chronic obstructive sialadenitis exhibiting metaplasia of intralobular ductal epithelium (×200)

Fig. 5

a SDC with prominent undulating lining representing collapse of previously distended cyst; true papillae with fibrovascular cores are not seen. b Collapsed ‘papillary oncocytic cystadenoma-like’ SDC with undulating cyst lining and uniform oncocytic metaplasia, but no papillae. c, d ‘Warthin tumor-like’ SDC with undulating cyst lining, uniform oncocytic metaplasia, and prominent lymphoplasmacytic inflammatory infiltrate subjacent to cyst lining