Fine-needle aspiration cytology of basal cell adenoma of the parotid gland: characteristic cytological features and diagnostic pitfalls.

We retrospectively studied the cytological features of aspiration cytology in 12 cases of basal cell adenoma (BCA) and 5 cases mistakenly diagnosed as BCA. On macroscopic findings, the 12 cases of BCA included 7 cases of solid type and 5 cases of cystic type. The characteristic cytological features of solid type BCA were three-dimensional clusters in 71%, sharp-angle small clusters in 86%, basement membrane- like material in 71%, and cell crush in 86%. In contrast, 3 of the 5 cystic type BCA cases showed inadequate cellular components or no basaloid tumor cells, and the cytological diagnosis of BCA could not be determined. In the 5 cases misdiagnosed as BCA, there were 2 cases of pleomorphic adenoma, 2 cases of benign lymphoepithelial cyst, and 1 case of basal cell adenocarcinoma. Accurate differential cytological diagnosis of BCA is relatively easy to determine the solid type BCA, but is more difficult for cystic type BCA.