Malignancy Analyses of Thyroid Nodules in Patients Subjected to Surgery with Cytological- and Ultrasound-Based Risk Stratification Systems

Abstract

The fine needle aspiration (FNA) cytology is the gold standard for the preoperative diagnosis of thyroid cancer. However, up to 30% of FNA examinations yield nondiagnostic or indeterminate results and this complicates patient management. Clinical features and ultrasound (US) patterns, including US risk stratification systems, could be useful in the preoperative diagnostic workup and prediction of malignancy, but the evidences are not univocal. Methods: 400 consecutive patients subjected to thyroid surgery were retrospectively enrolled at our institution in Calabria, Southern Italy. Preoperative US and FNA cytological descriptions, formulated according to the “Italian consensus for reporting thyroid fine-needle aspiration cytology” (ICCRTC) classification and three US risk stratification systems (those developed by the American Association of Clinical Endocrinologists, American College of Endocrinology and Associazione Medici Endocrinologi (AACE/ACE/AME), American Thyroid Association (ATA), and American College of Radiology (ACR-TIRADS)), were collected, along with histological results. Results: 147 thyroid cancer cases, in large majority papillary carcinomas, were detected on final histological examination. Almost two-thirds of patients subjected to thyroid surgery for either benign or malignant lesions were female. Patient’s age ≤20 years and between 21–30 years were clinical features associated with increased risk of thyroid cancer in logistic regression analyses. US features associated with thyroid cancer included irregular margins, solid composition, microcalcifications, and marked hypoechogenicity. The AACE/ACE/AME, ATA, and ACR-TIRADS risk categories, corresponding to specific US patterns, were strong predictors of malignancy in both genders, but not in nodules with indeterminate cytology. A measured difference between the longitudinal (L) and the anteroposterior (AP) diameter >5 mm, a proxy for a parallel-oriented oval shape of a nodule, emerged as a robust protective factor against thyroid cancer (OR 0.288 (95%CI 0.817–0.443); p < 0.001), regardless of cytological risk. Conclusions: Some, but not all, well-established predictors of TC have been confirmed in this study. Controversy surrounds the diagnostic performance of US risk stratification systems for the detection of thyroid cancer in the subgroup of nodules with indeterminate cytology, suggesting their use only to set the thresholds for FNA. A measured difference between L and AP diameters >5 mm may represent an additional and practical tool for ruling out malignancy in thyroid nodules, with the potential to reduce unnecessary surgical procedures.