Presentation
Left sided hearing loss.
Patient Data
A large T1 hypointense and T2 hyperintense circumscribed mass with diffuse vivid enhancement is present on the left. The mass is indistinguishable laterally from the deep lobe of the parotid, displaces the carotid arteries posteriorly, the parapharyngeal fat medially and anteromedially, and the medial and lateral pterygoid muscles anteriorly. The inferior portion of the mass inferiorly displaces the submandibular gland. The inner surface of the left mandibular ramus and angle is abutted but not invaded or destroyed. Mass-effect from this lesion also causes severe effacement of the oropharynx and nasopharynx and obstructs the left eustachian tube with mastoid effusion.
No perineural thickening or enhancement along the inferior alveoli, mandibular or facial nerve is identified. No cervical lymph node enlargement.
Conclusion The pattern of displacement suggests this is a mass arising from the deep lobe of the parotid, most likely a large pleomorphic adenoma.
Case Discussion
The patient went on to have a resection.
Histology:
The sections show a pleomorphic adenoma composed of confluent cords, nests and rare ducts lined by small discrete spindle cells and cuboidal cells devoid of nuclear atypia. The stroma appears myxoid with focal evidence of benign cartilage formation. Focally there is also squamous metaplasia. In areas at the periphery of the lesion there is a paucicellular fibrous capsule of varying thickness. A small amount of unremarkable salivary tissue is present at one edge of one fragment.
FINAL DIAGNOSIS: pleomorphic adenoma.
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