Pitfalls in Salivary Gland Fine-Needle Aspiration Cytology: Lessons From the College of American Pathologists Interlaboratory Comparison Program in Nongynecologic Cytology

Abstract

Abstract Context.—We use data from the College of American Pathologists Interlaboratory Comparison Program in Nongynecologic Cytology to identify common diagnostic errors in salivary gland fine-needle aspiration (FNA). Objective.—To identify salivary gland FNA cases with poor performance characteristics in the Nongynecologic Cytology Program surveys, so that the most common diagnostic pitfalls can be avoided. Design.—A retrospective review of the College of American Pathologists Nongynecologic Cytology Program's cumulative data from 1999 to 2003 revealed the most common false-positive and false-negative interpretations on FNA for common salivary gland lesions. Slides that performed poorly were then reviewed to identify the cytologic characteristics that may have contributed to their poor performance. Results.—A total of 6249 participant responses with general interpretations of benign (n = 4642) or malignant (n= 1607) were reviewed. The sensitivity and specificity of the participant responses for correctly interpreting the cases as benign or malignant were 73% and 91%, respectively. Benign cases with the highest false-positive rates were monomorphic adenoma (53% false-positive), intraparotid lymph node (36%), oncocytoma (18%), and granulomatous sialadenitis (10%). Malignant cases with the highest false-negative rates were lymphoma (57%), acinic cell carcinoma (49%), low-grade mucoepidermoid carcinoma (43%), and adenoid cystic carcinoma (33%). Selected review of the most discordant individual cases revealed possible explanations for some of the interpretative errors. Conclusions.—These data confirm the difficulty associated with interpretation of salivary gland FNA specimens. Cytologists should be aware of the potential false-positive and false-negative interpretations that can occur in FNAs from this organ site in order to minimize the possibility of diagnostic errors.