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case_images: Incidental finding on head MRI with coronal postcontrast fat saturated image of the brain (left) and T2 weighted image of the head (right) demonstrating avidly enhancing bilobed T2 hypointense lesion within the right parotid gland.
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case_images: MRI IAC was ordered to evaluate possible retrocochlear pathology, and a hypointense right parotid lesion measuring 1.8 x 2.1 cm was incidentally discovered (Figure 1).
case_images: The specimen was serially sectioned to reveal a multiloculated white to tan solid-cystic mass. The cut surface shows a cystic component (blue arrow) and the white nodular area (black arrow). The mass abuts the inked outer surface.
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case_images: Gross examination of the specimen revealed a multiloculated solid-cystic surface with yellow lobulated tissue in the periphery (Figure 2).
case_images: Histologic examination of the parotid mass shows multicystic lesions lined with bland epithelium containing pink amorphous material in the lumen (A, 40x; B, 200x) and ample lymphocytic infiltration in the stroma (B, 200x). There are multiple papillary infoldngs along the cyst walls with most devoid of mucous cells (C, 200x). However, several foci of mucinous-rich epithelium arranged in fused papillary structures are noted (D, 200x).
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case_images: On H&E section, multiple cysts lined by bland-looking cuboidal to columnar epithelium with lymphoid proliferation in the cystic wall are present (Figure 3(A) and (B)). Focal areas were lined by papillary infoldings (Figure 3, (C) and (D)) with scant to abundant mucous cells.
case_images: Tumor cells within an endothelial-lined structure is suspected, raising the possibility for lymphovascular invasion (A, 400x). The papilla with mucous cells also contains epidermoid cells on H&E (B, 200x) that stain positive for p63 (C, 200x) which supports the diagnosis of mucoepidermoid carcinoma.
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case_images: Rare groups of intermediate cells with round to oval nuclei and open chromatin are seen (Figure 4 (B)). P63 staining was performed to highlight the cyst wall lining and intermediate cell aggregates (Figure 4 (C)). An area of lymphovascular invasion was suspected, which suggested malignant nature (Figure 4 (A)).