Risk stratification of parotid neoplasms based on intraoperative frozen section and preoperative fine needle aspiration cytology.

PURPOSE: This study aims to determine the relationship of frozen section (FS) to final histology and determine how incorporating FS may change preoperative malignancy risk estimates based on preoperative fine needle aspiration cytology (FNAC). The secondary aim is to determine if FS is useful in influencing intraoperative decision-making. METHODS: Retrospective review of 426 intraoperative FS for parotidectomies performed for primary parotid lesions. RESULTS: Risk of malignancy with a benign FS was 2.5%, with indeterminate 36.1%, and with malignant 100%. Incorporating FS to fine needle aspiration for cytology helped to stratify malignancy risk especially in the Milan categories of atypia of undetermined significance, neoplasm of uncertain malignant potential and non-diagnostic categories, where a malignant FS increased malignancy risk significantly. FS was only able to identify 11% of high-risk histological subtypes for which a neck dissection would be recommended. CONCLUSIONS: FS may be used to stratify malignancy risk intraoperatively but has limited utility in clinical decision-making to perform a neck dissection and more extensive parotid resection in high-risk histological subtypes.

Risk stratification of fine-needle aspiration cytology of parotid neoplasms based on the Milan system-Experience from a tertiary center in Asia.

BACKGROUND: The recently described Milan system provides a unified way of categorizing salivary gland fine-needle aspiration (FNA) cytology. We aim to use this system to stratify risk of malignancy in parotid FNAs. METHODS: In this retrospective case series, 376 FNAs were preoperatively performed for 573 parotidectomies over 14 years. RESULTS: Risk of malignancy on FNA is as follows: nondiagnostic 14.5%, non-neoplastic 26.7%, atypia of undetermined significance 29.3%, benign neoplasm 2.7%, neoplasm of uncertain malignant potential 19.1%, suspicious for malignancy 87.5%, and malignant 100%. The specific diagnoses of pleomorphic adenoma and Warthin tumor on FNA have high positive predictive value of 97.5% and 96.6%, respectively. Multivariate regression associates smaller size of lesion with a nondiagnostic or indeterminate result. Seniority of operator is associated with a lower likelihood of a nondiagnostic result. CONCLUSIONS: This large Asian series validates the Milan system as a valuable tool in stratifying malignancy risk of parotid FNAs.