Prevalence of malignancy in thyroid nodules with AUS cytopathology: A retrospective cross-sectional study.

Background: Category III (AUS; Atypia of Undetermined Significance) of The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) was established to describe thyroid nodule features that are neither benign nor cancerous.

Objectives: This study aims to evaluate the rate of thyroid malignancy in patients diagnosed with AUS at the Armed Forces Hospital Southern Region (AFHSR), Saudi Arabia.

Method: The patients (508) diagnosed with AUS in their thyroid nodules underwent fine-needle aspiration cytology (FNAC). Data were collected through a chart-based approach, reviewing patients' medical records and relevant information.

Results: Among the cases, the majority were females (84.6%). Among the different age groups, individuals between 40 and 50 years had the highest prevalence of thyroid nodules (32.5%). Approximately 27% of patients exhibited tumor sizes larger than 4 cm. FNAC results revealed 16.5% benign, 26% AUS, and 22.4% follicular neoplasm cases. Histopathology indicated 54.1% of benign and 37.2% of malignant cases. Papillary carcinoma accounts for 80.4% of all malignant cases. A significant correlation was observed between FNAC and postoperative histopathology ( value < 0.05). Hypoechoic nodules exhibited 33.9% of malignant cases, and calcification was observed in 25% of the cases. A significant association was found between malignancy and echogenicity and between malignancy and calcification ( value = 0.003 and 0.001, respectively).

Conclusion: The findings of this study identify malignancy in thyroid nodules with AUS cytopathology, particularly in the Southern region of Saudi Arabia. The correlation between pre-surgery FNAC and postoperative histopathology supports FNAC's diagnostic value. Additionally, echogenicity and calcification can potentially contribute to predicting nodule malignancy.