Through our limited experience with cystic salivary gland tumors, FNA , gives fairly good  results, it is considered a good positive test to detect malignant tumors ,but when negative , you can not totatally exclude malignancy, 

Accurate subtyping of salivary gland lesions is not always possible with FNA. However in cystic lesions  the aim should be to diagnose whether neoplastic or non-neoplastic and favouring benign vs malignancy ,as in any case for neoplastic conditions surgery is done.Only the extent of surgery varies for benign and malignant neoplasms.Also intraoperative frozen section can sort out the problem in many of these cases.

Thanks so much for the responses.