Sialadenoma papilliferum of the bronchus: rare tracheobronchial tumor of salivary gland type.

Presented herein is the second case of sialadenoma papilliferum of the bronchus in a 75-year-old man. The bronchial tumor had an exophytic papillary lesion protruding into the lumen of the ostial region of the right superior lobe bronchus on chest CT and bronchoscopy. Grossly, the resected tumor was pedunculated, 5 x 3 x 3 mm in size and consisted of both an exophytic papillary lesion protruding into the bronchial lumen and a glandular component in the bronchial submucosa. Histologically, the papillary structures were lined by ciliated or non-ciliated columnar epithelium and metaplastic non-keratinizing stratified squamous epithelium. The submucosal glandular components were well circumscribed beneath and in continuity with the papillary lesion. The glandular components of cysts and duct-like structures were lined by a double-layer epithelium composed of luminal cells and basal cells. Sialadenoma papilliferum is a rarely recognized salivary gland tumor, mostly occurring at intraoral mucosal sites including the hard and soft palate and buccal mucosa. There have been sporadic cases of sialadenoma papilliferum of the esophagus, nasopharynx and nasal cavity. To the authors' knowledge only one case of sialadenoma papilliferum of the bronchus has been reported previously.