Crystalloids in FNA specimens of salivary gland lesions: A retrospective study in a single large institute.

Background Identifying crystalloids, which includes amylase and tyrosine crystalloids, is relatively uncommon in salivary gland fine-needle aspiration (FNA) cytology. Although it has been suggested that the presence of crystalloids favors a benign process, the full significance has not been well established. Methods The authors performed a review of slides from all salivary gland FNA cases received in their laboratory from January 2017 to September 2019 to identify cases with crystalloids (screened cohort). In addition, the departmental archives were searched retrospectively for all salivary gland FNA cases that had specifically reported crystalloids. Cytologic findings as well as correlation with surgical pathology and clinical follow-up were examined. Results There were 664 cases in the screened cohort. Crystalloids were present in 37 cases (incidence, 5.6%). Amylase crystalloids were the most commonly identified (n = 28; 75%), followed by tyrosine crystalloids (n = 4; 11%), and collagenous crystalloids (n = 1; 3%). Four cases with crystalloids could not be further classified because of low quantity (n = 4; 11%). An additional 54 cases were identified in the 10-year retrospective review. Diagnostic categorization for the total cohort (N = 91) was as follows: nondiagnostic, 30 cases (33%); nonneoplastic/benign, 42 cases (46%); neoplasm: benign, 10 cases (11%); and atypia of undetermined significance, 9 cases (10%). Twenty-six cases had subsequent resection findings, including oncocytic cyst/cystadenoma in 8 cases (31%), chronic sialadenitis/ductal obstructive change in 7 cases (27%), pleomorphic adenoma in 5 cases (27%), developmental cyst in 3 cases (12%), lymphoepithelial cyst in 2 cases (8%), and Warthin tumor in 1 case (4%). Conclusions This cohort represents the largest FNA series of salivary gland crystalloids. All cases were associated with nonneoplastic or benign neoplastic lesions.