Mucus retention cyst with development of basal cell adenoma: report of a case

Abstract

<h3>Background</h3> Mucus retention cyst is a relatively uncommon lesion of the salivary gland. Unlike the more common mucus escape reaction, it is a true cyst that is lined by epithelium consisting of a uniform layer of cuboidal to low-columnar cells. However, a uniform thin layer of nonkeratinizing stratified squamous epithelium is common, and occasional mucous cells within the epithelial lining of the cyst can be observed. Some authors have mentioned that in some cases the epithelium demonstrates papillary folds into the cystic lumen, when these lesions are misdiagnosed as papillary cystadenoma. Other authors contend that mucus retention cysts do not show piling up of cells in the wall of the cyst and neither proliferation nor infiltration of islands of epithelium into the connective tissue is a feature. These histologic features with connection to the absence of multicystic structures and of areas of solid epithelial proliferations are particularly important to rule out cystic neoplasms. Also, in the literature review, we could not find any reported case of mucus retention cyst with development of a neoplasm from the lining epithelium. <h3>Case report</h3> A 68-year-old man was referred to the Department of Oral Medicine and Oral Pathology of the Aristotle University Dental School, Thessaloniki, Greece, because of a painless swelling that periodically fluctuated in size. Intraoral examination revealed a well demarcated mass, soft to palpation, measuring 1.5 × 1cm, located in the submucosa of the upper lip. The covered mucosa was reddish-blue in color. Under local anesthesia the lesion was totally excised. Histologic examination showed the presence of a monocystic lesion lined by atrophic epithelium in proximity to normal minor salivary glands. Islands consisting of single layered cuboidal or columnar epithelial cells were also observed in contact with the lining epithelium and floating into the cystic cavity. These cell islands, when examined immunohistochemically, reacted positively in keratin 7 and S-100 protein and negatively for vimentin. <h3>Conclusion</h3> The histologic and immunohistochemical findings supported diagnosis of mucus retention cyst with development of basal cell adenoma. Differential diagnosis of the tumor is discussed.