Cytological and Ultrasound Features of Thyroid Nodules Correlate With Histotypes and Variants of Thyroid Carcinoma

Context Prognosis is excellent for papillary thyroid carcinoma (PTC), noninvasive follicular thyroid neoplasia with papillary-like nuclear features (NIFT-P), and follicular thyroid carcinoma (FTC) but is poor for poorly differentiated thyroid carcinoma (PDTC) and anaplastic thyroid carcinoma (ATC). Among PTCs, the prognosis is more favorable for follicular (FV-PTC) and classic (CV-PTC) than for tall cell (TCV-PTC), and solid (SV-PTC) variants. Objective To associate histotypes and variants of thyroid carcinoma with ultrasound and cytological features. Methods Histology of 1018 benign tumors and 514 PTC (249 CV, 167 FV, 49 TC, 34 SV, and 15 other variants), 52 NIFT-P, 50 FTC, 11 PDTC, and 3 ATC was correlated with fine-needle aspiration biopsy categories (Italian classification: TIR1, TIR2, TIR3A, TIR3B, TIR4, and TIR5) and ultrasound features at the Endocrinology Unit, University Hospital of Pisa. In total, 1117 patients with thyroid nodule(s) who underwent thyroidectomy were included. Results Of PTC, 36.3% had indeterminate cytology (TIR3A or TIR3B), 56.6% were suspicious for malignancy or malignant (TIR4 or TIR5); 84.0% FTC and 69.3% NIFT-P were TIR3A or TIR3B; 72.5% FV-PTC and 73.6% SV-PTC were TIR3A or TIR3B; 79.9% CV-PTC and 95.9% TCV-PTC were TIR4 or TIR5. The association of a hypoechoic pattern, irregular margins, and no microcalcifications was more frequent in TCV-PTC than in CV-PTC (P = .02, positive predictive value = 38.9%; negative predictive value = 85.5%). Conclusion At cytology, most FTC, NIFT-P, FV-PTC, and SV-PTC were indeterminate, most CV-PTC and TCV-PTC were suspicious for malignancy or malignant. Ultrasound can be helpful in ruling out TCV-PTC.