Incidental finding of a left parotid lesion during MRI for a pituitary adenoma.
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Within the tail of the left parotid gland is a large lesion measuring 3.2 x 2.2 by 2.4 cm. It is of intermediate low signal on T1, of heterogeneous and high signal on T2 with central regions of low signal, and has poorly defined margins.
On post-contrast sequences demonstrates heterogeneous but vivid enhancement, with a central poor enhancement corresponding to the low T2 components. It is located superficial to the retro mandibular vein, which is displaced around its medial margin.
Inferiorly and especially medially, no normal parotid tissue can be seen between the mass and adjacent fat.
Large pituitary mass is noted incidentally. The remainder of be neck appears unremarkable.
Large left parotid mass has indeterminate imaging features, but ill-defined margins raises possibility of it being malignant. High T2 signal can be seen in mucoepidermoid carcinoma, Warthin's tumour, and a pleomorphic adenoma.
Left parotid: A parotid with two orienting sutures, a short presumed anterior and long presumed medial. The specimen measures superior to inferior 60mm, medial to lateral 30mm and anterior to posterior 30mm. There is a firm lobulated tumour measuring at least 35mm in maximum dimension. The tumour has a gristly cut surface and is pale white.
Parotid gland: The sections show parotid tissue in which an encapsulated pleomorphic adenoma is seen. The tumour consists of epithelial and stromal components. The stromal component is dominant and includes myxoid, fibrous, chondroid and cartilaginous areas. No atypia of the stroma component is seen. The epithelial component is unevenly distributed but includes islands and cords of bland epithelioid cells in which squamous differentiation, keratin filled cysts and glandular structures are seen. Foci of plasmacytoid cells are seen. No significant cellular atypia is identified. Areas of dystrophic calcification are also seen. The capsule abuts multiple inked surgical margins.
Left parotid: Pleomorphic adenoma with capsule abutting inked surgical margins
Key learning points:
- pleomorphic adenomas >2 cm can demonstrate heterogeneous signal