BACKGROUND: The diverse range of diseases that affect the salivary glands may lead to problems and pitfalls in cyto-diagnosis. While false negative diagnosis of cystic salivary gland tumors is well known, false positive cytodiagnosis in nonneoplastic salivary cysts is less well documented.
CASE: An 85-year-old female presented with a painless left parotid gland swelling of three months' duration. Fine needle aspiration cytology yielded fluid, smears of which showed keratinizing squamous cells with nuclear atypia leading to a cytologic diagnosis of cystic squamous cell carcinoma. A total radical parotidectomy followed. Histopathologic study showed cystic dilatation of many of the salivary ducts, which were lined with metaplastic squamous epithelium that showed atypia. There was no evidence of squamous cell carcinoma.
CONCLUSION: Squamous metaplasia is known to occur in benign salivary gland lesions, such as pleomorphic adenoma and Warthin's tumors, as well as in salivary duct cysts and necrotizing sialometaplasia. However, atypical squamous metaplasia of salivary duct cysts mimicking squamous cell carcinoma on cytology is unusual.