Fine-needle aspiration of the thyroid: A cytohistologic correlation with critical evaluation of discordant cases

Background: There is some gray zone of thyroid cytology, where the diagnostic efficacy declines sharply rendering it difficult to exactly categorize the lesion resulting in discrepancy. The aim of the study is to assess the accuracy of fine needle aspiration of the thyroid and critically evaluate the cytohistological discordant cases. Materials and Methods: A total of 447 patients with thyroid swelling were aspirated during a seven-year study period. Cases showing cytohistologic disparity were reevaluated for the detection of possible causes of failure. Results: In our study, cytohistologic concordance was achieved in 80.28% of the cases. Of the discordant cases, false positives accounted for 11.60% and false negatives for 9.8%. Suboptimal material and underdiagnosis of papillary carcinoma due to cystic degeneration were recognized as common pitfalls. Too much emphasis on cellularity and architectural pattern led to the erroneous false positive diagnoses. Conclusion: Strict adherence to adequacy criterion and meticulous examination of all the smears are of paramount importance in reducing discrepant cases.