Pitfalls in the fine needle aspiration cytology of the neck lymph node

Abstract

Fine-needle aspiration cytology (FNAC) is a highly accurate tool for the diagnosis of pleomorphic adenomas. However, this common salivary gland neoplasm can be diagnostically challenging, causing pitfalls in cytodiagnosis because ectopic salivary gland tissue is relatively common in cervical lymph nodes, particularly near the parotid gland. Any of them, therefore, may be the source of salivary gland tumors, or may be confused with metastasis (by finding extraneous tissue in an unexpected site). If pleomorphic adenomas with papillary features stem from ectopic salivary glands in the neck region or other ectopic locations, they may be easily mistaken for metastatic papillary carcinoma, particularly if the aspiration smears only show the papillary components composed of cells with hyperchromatic, pleomorphic, and crowded nuclei. Foci of squamous metaplastic changes may occur in pleomorphic adenomas. Similarly, if pleomorphic adenomas or other benign salivary gland lesions with extensive squamous metaplasia are found in the neck region or other ectopic locations, they may be easily mistaken for metastatic well-differentiated squamous cell carcinoma, particularly when the aspiration smears are primarily composed of squamous metaplastic components. We have been confronted with both type of cases and are willing to share with colleagues.