Validity of fine needle aspiration cytology in diagnosing thyroid gland neoplasms

Objectives: To determine the validity of Fine needle aspiration cytology (FNAC) in diagnosing thyroid neoplasms and to identify the causes of false positive and negative results.

Method: Thyroid FNACs of 100 patients with subsequent histology were analysed. The diagnostic categories used included Thy 1 to Thy 5. Thy 3 was subdivided into Thy 3a and Thy 3b depending on the presence or absence of features suggestive of a follicular neoplasm. Histology results were categorized as neoplastic or non neoplastic. Results of FNACs were correlated with histology.

Results: FNAC predicted the presence of neoplasms with a sensitivity of 77.7.8%, specificity of 83% and had a diagnostic accuracy of 90%. The false negative rate was 8% and the cause was non diagnosis of impalpable papillary micro carcinomas.

Conclusion: Sensitivity could be increased by ultrasound scan guided aspiration in non palpable lesions. Sub categorization of Thy 3 into a and b increases the specificity of FNAC in detecting thyroid malignancy.

DOI: http://dx.doi.org/10.4038/jdp.v6i1.4424

Journal of Diagnostic Pathology 2011(6); 1: 34-41