Salivary gland FNA cytology: role as a triage tool and an approach to pitfalls in cytomorphology.

Abstract

To highlight the importance of salivary gland fine needle aspiration (FNA) cytology as a triage tool for surgery and to determine its sensitivity and specificity. To discuss the diagnostic pitfalls and potential role of ancillary techniques in diagnosis and prognosis. The study included a total of 920 cases of salivary gland FNAs received in the cytopathology department of University College London Hospital during December 2004 to December 2012. The cases with known histological outcomes were analysed to determine the sensitivity and specificity. Surgery was carried out on 180 (19.6%) of 920 patients. Excluding nine with inadequate/non-diagnostic cytology, the sensitivity of FNA cytology for a malignant outcome was 89% (33/37) and the specificity was 97% (130/134). Diagnostic pitfalls are discussed with respect to eight FNAs with discrepant histology. Histological outcome was not available for 740 cases (80.4%): excluding 88 non-diagnostic FNAs, 324 (49.7%) had non-neoplastic diagnoses (not indicating surgery) and 328 (50.3%) had neoplastic diagnoses, which included recurrences/metastases of known tumours. Patients with other neoplasms on FNA were lost to follow-up and may have had surgery elsewhere. Cases with clinical concerns were discussed at weekly multidisciplinary meetings. Salivary gland FNA is crucial in the distinction of non-neoplastic from neoplastic lesions, emphasizing the fact that FNA is an excellent triage tool for surgery. Salivary gland FNA has a high sensitivity and specificity. However, it is important to interpret the cytological diagnoses in the light of clinical findings and imaging. Diagnostic pitfalls are seen in a minority of cases and could potentially be overcome with the help of recently described diagnostic and prognostic markers.