Role of AgNORs in thyroid lesions on fine needle aspiration cytology smears

Background: Fine needle aspiration has an important role in diagnosis of thyroid neoplasm. However, it is difficult to differentiate between follicular adenoma and follicular carcinoma by cytology alone. Recently, silver staining has been performed for nucleolar organizer regions (AgNORs) to differentiate various tumors. Aims: The present study was undertaken to see if the AgNOR technique could distinguish between benign and malignant lesions, particularly, follicular neoplasm. Materials and Methods: One hundred forty cases of thyroid lesions were examined, which included colloid goiter (n = 36), multinodular goiter (n = 38), subacute thyroiditis (n = 6), Hashimoto′s thyroiditis (n = 17), lymphocytic thyroiditis (n = 3), follicular neoplasm (n = 18), Hurthle cell neoplasm (n = 3), papillary carcinoma (n = 16), and medullary carcinoma (n = 3). Diagnosis was confirmed by histopathology in 80 cases. The usual one-step silver colloidal reaction was performed at room temperature for 35 minutes and intranuclear dots of silver deposits were counted in 100 cells. Results: AgNOR counts of benign and malignant lesions were compared and were found to be statistically significant (P < 0.001). The mean AgNOR counts were higher in neoplastic lesions. Conclusions: AgNOR counting in fine needle aspiration smears is a simple, sensitive, and cost-effective method for differentiating benign from malignant thyroid follicular neoplasms