Tumor/Nodule Size Ratio: A Possible Reason for False-Negative Thyroid Cytology

Introduction: Fine-needle aspiration cytology is useful for the diagnosis and management of thyroid nodules. However, false negatives for malignancy may occur and affect treatment success. In this study, we investigated carcinoma size itself as another possible reason for false-negative results. Methods: We retrospectively reviewed patient charts who had undergone total thyroidectomy and complementary thyroidectomy. A total of 613 cases were investigated. Patients who had a final histopathological diagnosis of thyroid carcinoma were included, and 138 cases were eligible for the study. Patients were categorized into three groups according to their fine-needle aspiration biopsy reports: Benign cytology and atypical cells of undetermined significance (group 1), cytology suspicious for a follicular/Hurthle cell neoplasm (group 2), and suspicious or positive for malignancy (group 3). Results: Group 1 consisted of 55 patients with a mean tumor/nodule size ratio of 0.5236. Group 2 consisted of 21 patients with a mean tumor/nodule size ratio of 0.76. Group 3 consisted of 62 patients with a mean tumor/nodule size ratio of 0.848. There were no differences between the groups in terms of nodule size measured by ultrasonography (p=0.209), but the diameter of the carcinoma focus within the nodule was significantly smaller in false-negative cases (p<0.001). There were no statistically significant differences between the groups in terms of multicentricity (p=0.197). Conclusion: The size of malignant tumors may be more important than nodule size in explaining false negativity. ABSTRACT