Schwannoma-like pleomorphic adenoma: a case report with review of the literature.

Pleomorphic adenoma is a common benign salivary gland tumor, which represents about 66 % of benign neoplasms of the salivary glands. Although it can occur in any salivary gland, it is most frequently found in the parotid. Pleomorphic adenomas are renowned for their cytomorphological and architectural heterogeneity that are characterized by intermixed epithelial and mesenchymal-like components. We report a rare case of pleomorphic adenoma of the parotid gland with prevalent schwannoma-like features mimicking a benign schwannoma. Microscopically the tumor showed a prevalence (about 95 %) of schwannoma-like areas with focal (about 5 %) epithelial component with tubular organization. The tumor showed positive immunoexpression for cytokeratin, S-100 protein, and focal expression of p63, CD10 and smooth muscle actin. To the best of our knowledge only six cases of schwannoma-like pleomorphic adenoma have been reported in the literature. The differential diagnosis between this entity and neurogenic and myogenic tumors is discussed.