A cell pattern approach to interpretation of fine needle aspiration cytology of thyroid lesions: A cyto-histomorphological study

Aim: Our study aimed at a cell pattern approach to interpret thyroid cytology and to demonstrate diagnostic accuracy of fine needle aspiration cytology (FNAC) with an emphasis on diagnostic pitfalls. Materials and Methods: A total number of 218 goitre cases, from the year 2000 to 2004, were reviewed retrospectively from the cytology files, without considering the previous cytological diagnosis. Four cases with inadequate aspirate were excluded. The predominant cell pattern, such as macro/normofollicular, microfollicular, papillary, syncytial, dispersed and cystic pattern, was noted in each case. The final diagnosis was arrived by observing the cellular details and background elements. Cytological diagnosis was correlated with histopathology in 75 cases. The sensitivity and specificity were computed. Results: Normo/macrofollicular pattern was seen in 71.96% of nodular goitre and 6.9% of follicular neoplasms. Around 86.2% of follicular neoplasms and 17.6% of papillary carcinoma had microfollicular pattern. The papillary pattern was seen in 47% of papillary carcinoma. Syncytial pattern was noticed in 72.3% of chronic lymphocytic thyroiditis and 29.4% of papillary carcinoma. Cytological diagnosis was concordant with histopathological diagnosis in 65 cases. Overall sensitivity and specificity of FNAC in diagnosing neoplastic lesions of thyroid were 83.33 and 95.55%, respectively. Conclusion: FNAC is more sensitive and specific in triaging neoplastic from non-neoplastic thyroid lesions. Identification of the predominant cell pattern would be complementary to analysis of cell morphology and background details in cytological diagnosis of thyroid lesions. This approach helps to diagnose follicular neoplasm and follicular variant of papillary thyroid carcinoma.