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Keywords:
Cyst containing keratin, keratin pearls, minor salivary glands, myoepithelial cells, pleomorphic adenoma, squamous metaplasia
Abstract
The presence of numerous keratin pearls on microscopic study is a feature commonly seen in well-differentiated squamous cell carcinoma. Pleomorphic adenoma (PA) can show the presence of squamous metaplasia with keratin pearls as a rare finding. Here, we present a case of a male patient in the 5th? decade presenting with a mass? on the buccal mucosa who smokes tobacco. On microscopic study, the mass showed tumor cells presenting with extensive keratin pearl formation. In this paper, we want to highlight the rare findings of extensive keratin in PA of minor salivary glands, the significance of special stains in diagnosis and differential diagnosis of this uncommon presentation.
Introduction
Pleomorphic adenoma (PA) involving the minor salivary glands is in the range of 38-44%. As far as minor glands are concerned the palate, upper lip and buccal mucosa are the most common sites for PA. The hallmark of PA is the histologic diversity which has mixed histology and is composed of an epithelial and a stromal/mesenchymal component. Here, we present an unusual case of PA with extensive squamous metaplasia and keratin pearl formation in a minor salivary gland with microscopic features, significance of special stain in diagnosis, and the differential diagnosis of this unusual presentation. Reports of PA presenting with multiple and large squamous epithelium-lined keratin cysts along with squamous metaplasia are sparse.
Case Report
A male patient aged 50? years presented with a slow-growing, asymptomatic leftcheek swelling of 3? years duration. History revealed he smokes 4 packs/day for 30? years. On clinical examination, the findings observed were a single, well-defined swelling of size 4? cm × 4? cm firm, mobile mass in the leftbuccal mucosa extending anteriorly 2? cm distal to the angle of the mouth and posteriorly up to the first permanent molar region [Figure 1]. The mass was excised completely under local anesthesia. While performing the incision, care was taken to avoid injury to the parotid duct opening located on the surface of the buccal mucosa, opposite the upper second molar tooth. As the mass did not involve the facial muscles or the subcutaneous tissue of the cheek, wide local excision with satisfactory margins was performed. Clinically,...