Perineurioma of the parotid gland: first case report

Neurogenic neoplasms account for approximately 1% of salivary gland tumors. A 45-year-old woman presented with a slowly growing unilateral parotid gland mass that was excised completely by lateral parotidectomy. No recurrence was detectable 6 months after surgery. The resection specimen contained a 1.7 × 1.2 × 1-cm whitish nodular lesion that was firm, well circumscribed, and completely surrounded by compressed normal glandular tissue. The tumor was composed of spindle cells with bipolar tapering, wavy nuclei, and palely stained cytoplasm. The tumor cells were arranged in storiform, lamellar, and whorled patterns. Nuclear atypia, necrosis, and significant mitotic activity were absent. Immunohistochemistry showed expression of epithelial membrane antigen, glucose transporter 1, claudin-1, and collagen IV. All other lineage-specific markers including protein S100 were negative in the tumor cells. To our knowledge, this case represents the first report of soft tissue perineurioma in the salivary gland. Lack of previous reports suggests underrecognition of this tumor entity at this unusual anatomical site.