Epithelioid schwannoma of the facial nerve masquerading as pleomorphic adenoma: a case report.

Schwannomas arising in the parotid gland or peri-parotid region is frequently misdiagnosed as pleomorphic adenoma on cytologic preparations. The epithelioid variant of schwannoma is particularly susceptible to misdiagnosis because this neoplasm typically has epithelioid and spindled cells, which are associated with fibrillar stroma and mimic the epithelial, myoepithelial, and stromal components of a pleomorphic adenoma. Preoperative diagnosis of schwannoma is critical in order to plan appropriate management and to avoid inadvertent injury to the associated nerve during surgical resection. Thus, awareness of the distinct clinical, radiological, and cytomorphological features of schwannoma is important in order to guide clinical management. If the cytomorphological features are equivocal, immunohistochemical staining may provide a valuable alternative for distinguishing between pleomorphic adenoma and schwannoma.