Diagnostic challenges and problem cases in salivary gland cytology: A 20-year experience

BACKGROUNDFine-needle aspiration (FNA) is routinely performed to evaluate salivary gland lesions, and provides valuable information regarding the cytomorphologic features of the lesions. Occasionally, there are overlaps between benign and malignant conditions due to heterogeneity of the cell types, metaplastic changes, and sampling issues. Herein, the authors present a retrospective study of diagnostic pitfalls in salivary gland cytology and the simulating conditions. METHODSA 20-year retrospective review (1995-2015) of medical records was performed searching for the cytology reports of patients who underwent FNA of the salivary gland with the words amendment or revision. Medical records of the revised cases were reviewed for the subsequent surgical follow-up. All cases with a diagnostic discrepancy between the primary cytologic diagnosis and the final histology diagnosis were included in the current study. The histologic diagnosis was considered the gold standard. RESULTSA total of 19 cases were included in the current study. The cases were divided into 7 categories based on their cytologic diagnoses: 1) nondiagnostic (1 case); 2) benign, nonneoplastic lesion (2 cases); 3) benign salivary gland neoplasm (2 cases); 4) salivary gland neoplasm (4 cases); 5) epithelial neoplasm, not otherwise specified (1 case); 6) markedly atypical cells suspicious for a malignant neoplasm (1 case); and 7) malignant neoplasms (8 cases). CONCLUSIONSThe interpretation of salivary gland FNA can be influenced by several factors including prominent metaplasia, focal atypia, cystic changes, variable cellular components within the lesions, scant cellularity, variants of neoplasms, and a prior history of malignancy. Multiple passes representing the entire mass, imaging findings, and familiarity with salivary gland cytomorphology may improve the diagnostic accuracy. Cancer Cytopathol 2018;126:101-11. (c) 2017 American Cancer Society. Salivary gland cytology can be challenging due to a large variety of both benign and malignant neoplasms, the heterogeneity of the cells composing the tumors, the presence or absence of matrix, the presence or absence of lymphocytes, and even tissue sampling. The results of a 20-year search of salivary gland fine-needle aspiration cases in a large academic institution demonstrate that pleomorphic adenoma, mucoepidermoid carcinoma, oncocytic lesions, lymphocyte-rich lesions, and lesions with prominent squamous cell features are the most common causes of misdiagnoses.