Most malignancies identified by thyroid fine-needle aspiration (FNA) are papillary thyroid carcinoma (PTC). This study sought to determine if clinically adverse features of PTC correlate with the preceding cytologic diagnosis.
Thyroid FNA diagnoses were correlated with subsequent histopathologic findings.
From 6175 thyroid FNAs, histologic follow-up confirmed PTC in 52 of 184 (28%) FNAs with atypia of undetermined significance (AUS), 52 of 190 (27%) FNAs suspicious for follicular neoplasm, 182 of 229 (79%) FNAs that were suspicious for malignancy, and 188 of 198 (95%) FNAs that were malignant (M). Sex, age, and disease multifocality did not differ among FNA diagnosis groups. However, PTCs following an M FNA were more likely to have a higher American Joint Committee on Cancer T and N stage, and have lymphovascular invasion and/or extrathyroidal extension. Two patients had distant metastasis at initial surgery, whereas 16 developed subsequent recurrence and/or metastasis; all had a preceding M FNA. High-risk histologic subtypes of PTC also stratify to the M category, accounting at least partly for the association of cytologic diagnosis with adverse pathological parameters. Conversely, follicular variants of PTC predominate in non-M categories.
The Bethesda System for Reporting Thyroid Cytopathology conveys malignancy risk, but also predicts the presence of pathological risk factors and disease progression when the malignancy is PTC. M diagnoses identify higher risk PTCs, whereas AUS diagnoses identify low-risk PTCs, mostly follicular variants. These findings support the concept of conservative clinical management for some patients with AUS, while suggesting that a central neck dissection may be routinely justified in some patients with a M FNA.