Fine-needle aspiration cytology of pleomorphic adenoma: cytologic variations and diagnostic pitfalls: a report of two cases.

ABSTRACT

Introduction: Fine-needle aspiration cytology (FNAC) of the salivary gland is a sensitive and specific technique used in the diagnosis of lesions of the salivary gland. On FNA, adequately cellular aspirates make distinction easy in most cases. However, sparse cellularity makes diagnosis difficult partly due to lack of observer familiarity with the different patterns. The diagnosis of pleomorphic adenoma (PA) can be made accurately but this common salivary gland neoplasm can be diagnostically challenging, causing pitfalls in cytodiagnosis. Material And Methods: A 26-year-old male presented with a firm, painless, mobile slowly-growing mass in the right preauricular region of three years duration. Fine needle aspiration (FNA) was done. A diagnosis of pleomorphic adenoma suspicious of malignancy was given due to the presence of isolated squamous cells, occasional cluster of basaloid cells, occasional giant cells and hyaline globules. Histology confirmed a pleomorphic adenoma with marked squamous metaplasia and keratin cyst formation without evidence of malignancy. A 52-year-old male presented with a firm, painless, mass in the right preauricular region of five months duration. FNAC smears were cellular and showed a hemorrhagic background. Numerous single anucleate and nucleate squamous cells, myoepithelial cell clusters and epithelial cell aggregates were seen. Few foamy cells, giant cells and hyaline globules were noted. Characteristic metachromatic fibrillary chondromyxoid stroma which is usually seen in pleomorphic adenoma was absent. A diagnosis of pleomorphic adenoma suspicious of malignancy was given. The patient was lost to follow up and hence details regarding the histopathological status of his preauricular swelling were not known. Results: Here we illustrate that PA with squamous metaplasia, basaloid cells and hyaline globules can be misinterpreted as carcinoma on cytology and discuss the various pitfalls of cytology. Conclusion: FNAC is a good pre-operative procedure for the diagnosis of PA. One should be aware of the cytological variations to avoid diagnostic errors. When one is uncertain about classification of a salivary gland tumour the cytopathologist should leave the diagnosis open with a few suggested differential diagnoses rather than issuing a misleading report.