Context: Thyroid fine needle aspiration cytology (FNAC) is used extensively to identify the nodules that require surgery and helps to decrease the overall incidence of thyroidectomy in patients with benign disease. Aim: The aim of this study was to study the various cell patterns, the cellular details and background elements observed in FNA smears of thyroid lesions and to correlate with the histological diagnosis. Settings and Design: This retrospective study was conducted in the Department of Pathology, Sree Balaji Medical College & Hospital, Chennai. Methods and Material: 148 FNAC slides of thyroid lesions were studied for the predominant cell pattern, cell morphology and background. The cell patterns observed were Normofollicular/Macrofollicular, Microfollicular, Papillary, Syncytial, Dispersed and Cystic. The cytological diagnoses were compared with the histopathological diagnosis wherever possible. Histopathology was available for 86 cases. Statistical analysis used: The results were tabulated and analysed with IBM SPSS version 20. Results: The correlation between predominant cell pattern, cell type and background with the histopathology, using Kendall tau-b Correlation and Kappa Measure of Agreement (κ), was high. Conclusions: We conclude that analysis of the predominant cell pattern in combination with the cellular morphology and background, serves as a valuable tool for the interpretation of fine needle aspirates of thyroid lesions.

Keywords: Thyroid; Cell Pattern; Follicular; Papillary; Syncytial; Cystic.