Role of Fine Needle Aspiration and Frozen Section in the Diagnosis of Thyroid Lesions .

Abstract

The study compares fine needle aspiration cytology and frozen section of thyroid to final histopathologic diagnosis and characterizes the pitfalls in their use. Material and Methods : FNAC and FS were evaluated in 50 patients who underwent a thyroid surgery. Accuracy of FNAC and FS were assessed by definitive histological section as reference. Sensitivity, specificity, positive predictive value and negative predictive value were calculated for both FS and FNAC. Results. On frozen section evaluation 9 0f the13 (69.2%) malignancies could be diagnosed . Of the 6 deferred diagnosis only 2 turned out to be malignant on histopathology No false positivity was reported with frozen section while. False negativity was seen in 2 cases. Fine needle aspiration cytology was able to detect only 6 out of 13 malignant cases where as 10 were labelled as suspicious and 2 showed inadequate cellularity. Two of the 4 cases missed on frozen section were papillary microcarcinomas. The other 2 cases were follicular carcinoma where capsular and vascular invasion could not be demonstrated on frozen section. Sensitivity, specificity and accuracy of frozen section was reported to be 81.8%, 100% and 95.4% respectively as compared to 60%, 100%, and 89.4% of that of FNAC. Conclusion. Frozen section evaluation remains a useful tool, complimentary to FNAC. Frozen section can be avoided when the FNAC is consistent with benign or malignant, but could be of value (i) When FNAC result is reported as suspicious or inadequate. (ii) In diagnosis of unsuspected nodule found at surgery.