Pleomorphic adenoma of salivary gland: to what extent does fine needle aspiration cytology reflect histopathological features?

OBJECTIVE: The histological diversity encountered in pleomorphic adenoma may cause diagnostic difficulty in fine needle aspiration (FNA) cytology due to limited and selective sampling. The present study based on 25 histologically confirmed pleomorphic adenoma cases attempts to find out to what extent FNA cytology reflects the histopathological features. METHODS: May-Grunwald-Giemsa and Papanicolaou stained smears, and haematoxylin and eosin stained paraffin sections of 25 pleomorphic adenomas of parotid and submandibular glands were reviewed. The cellularity, which was assessed in a sliding scale of 1+ to 4+, and proportions of epithelial to mesenchymal components in FNA smears and histology was determined and compared. The frequency of morphological features such as squamous metaplastic cells, cells with oncocytic change, acinus formation, mucus globules, papilla formation, giant cells, myxoid and chondroid matrix as well as specific nuclear features was compared between the two diagnostic methods, and the statistical significance was determined using Fisher's exact test of probability. RESULTS: There was complete concordance between cytology and histology with respect to overall cellularity in 14 (56.0%) cases and in the proportions of epithelial to mesenchymal components in 13 (52.0%). Epithelial cells and myxoid matrix were present in all cases. There was no significant difference between smear and tissue section with respect to frequency of squamous metaplasia, oncocytic change, acinus formation, papilla formation, mucus globules, giant cells, nuclear pleomorphism, nuclear chromatin pattern, and mitotic figures. Morphological parameters that were significantly higher in FNAC compared with histology included intranuclear cytoplasmic inclusions (36.0% versus 8.0%, p = 0.0374), nuclear grooves (84.0% versus 48.0%, p = 0.0090), and reniform nuclei (20.0% versus 0.0%, p = 0.0502). Chondroid matrix was the only parameter which was significantly more common in histology than in cytology (44.0% versus 4.0%, p = 0.019). CONCLUSION: FNA cytology demonstrates well most of the histological features of pleomorphic adenoma of salivary gland and may be considered a useful tool in initial assessment of the tumour.