PMC5525067_01
Intraoral aspect of the lesion located in the left posterior buccal mucosa near the retromolar triangle. The clinical examination revealed a yellowish well-circumscribed, movable submucosal mass of approximately 21 x 15 mm in diameter, covered by a normal mucosa.
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The overall clinical appearance of the mass suggested a benign lesion (Figure 1).
Low-power magnification of the resected specimen measuring roughly 19 x 13 x 8 mm, showing an encapsulated solid lesion characterized by a multilocular cystic space with fibrous tissue lined by a stratified epithelium. In the cystic lumen, proteinaceous fluid is present (haematoxylin and eosin; original magnification x10).
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In the cystic lumen, proteinaceous fluid was present (Figure 2).
More details of the cystic wall composed of fibrous tissue with its surrounding stroma containing microvessels and apocrine-like secretory epithelium consisting of epithelial sweat-duct-like lining without cytologic atypia (haematoxylin and eosin; original magnification x200).
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Microscopically, the lesion consisted of a cystic wall lined by two or more rows of sweat-duct-like epithelium, with monomorphous cubic cells characterized by a small, central nucleus and without cytologic atypia (Figure 3).
Higher magnifications of the cystic wall composed of a stratified apocrine-like secretory epithelium consisting of epithelial sweat-duct-like lining without cytologic atypia. Rows of secretory cells showing decapitation secretion characterized by apocrine snouts and fringes are clearly recognizable (haematoxylin and eosin; original magnification x400).
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The cubic cells showed decapitation secretion indicative of apocrine secretion (Figure 4).
Histopathological staining. (a) Periodic Acid Schiff histochemical staining, showing PAS-positive content of the cyst (original magnification x50); (b) mucicarmine staining highlighting the mucinous content of the lesion (original magnification x50); (c) human epidermal growth factor receptor 2 immunohistochemical staining, showing diffuse cytoplasmic expression and confirming the secretory nature of the epithelial lining (original magnification x200); (d) smooth muscle actin immunohistochemical staining highlighting myoepithelial cells (original magnification x200).
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The lesion was then subjected to immunohistochemical staining to support the diagnosis (Figures 5(a)-5(d)).