The Analysis of Indeterminate Category in Thyroid Fine Needle Aspiration

Background : Descriptive diagnosis reports have been causing some problems in communication. Our institution decided to use the category diagnosis system since June, 2008. So we evaluated the effectiveness of this change. Methods : The category system is composed of unsatisfactory, suboptimal for diagnosis but suggestive of, most probably benign, indeterminate, suspicious for malignancy and malignancy. We evaluated 1,525 cases from June, 2008 to September, 2009. We analyzed 159 cases of the indeterminate category. Results : Among the 159 cases, 21 were re-aspirated and 63 underwent an operation. The diagnoses of the re-aspirated cases were 2 positive for malignancy, 5 indeterminate, 13 most probably benign, and 1 unsatisfactory. The surgical diagnoses were 39 malignancies, 2 follicular adenomas and 1 Hurthle cell adenoma, and 21 benign lesions. Re-aspiration for the indeterminate cases could help decide whether the lesions need to be operated or not at above 70%. The indeterminate category could predict the surgical diagnosis of the thyroid nodule with statistical significance when the subcategories were indicated (p < 0.001). Conclusions : The category diagnosis is replacing the descriptive diagnosis for the thyroid fine needle aspiration. The indeterminate category is useful and effective for making the decision to operate and especially when the indeterminate subcategories are used.