Features associated with locoregional spread of papillary carcinoma correlate with diagnostic category in the Bethesda System for reporting thyroid cytopathology.

BACKGROUND: 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.
METHODS: Thyroid FNA diagnoses were correlated with subsequent histopathologic findings.
RESULTS: 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.
CONCLUSIONS: 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.