Risk factors for central neck lymph node metastases in follicular variant vs. classic papillary thyroid carcinoma.

PURPOSE: Histological variants of papillary thyroid carcinoma (PTC) have been advocated as possible risk factors for central neck nodal metastases (CNM). A lower incidence of CNM in follicular variant of papillary thyroid carcinoma (fvPTC) when compared with classic PTC (cPTC) has been observed. We aimed to compare risk factors for CNM in patients with fvPTC and cPTC.

METHODS: The medical records of 1737 patients with a diagnosis of cPTC or fvPTC were reviewed. Demographic, clinical and pathological findings were prospectively registered. Risk factors for CNM were evaluated by univariate and multivariate analysis in cPTC vs. fvPTC patients.

RESULTS: Six hundred and fifty-two patients (37.5%) had fvPTC. The diagnosis was incidental in 69.5% of the fvPTC and in 29.4% of the cPTC patients. Overall, 26.3% cPTC and 8.3% fvPTC patients showed CNM (p < 0.001). In both cPTC and fvPTC patients at univariate analysis age <45 years, nonincidental diagnosis, tumor size >5 mm, multifocality, angioinvasion and extracapsular invasion were risk factors for CNM. At multivariate analysis independent risk factors for CNM in both cPTC and fvPTC patients were age <45 years (p < 0.01), nonincidental diagnosis (p < 0.001), multifocality (p < 0.001) and extracapsular invasion (p < 0.001).

CONCLUSIONS: No differences were observed between cPTC and fvPTC with regard to risk factors of CNM. fvPTC seems associated with a lower incidence of CNM, presumably because of the higher rate of incidental diagnosis. With the exception of age, in patients with a preoperative diagnosis of PTC, no preoperatively available clinical parameter is a reliable predictor of CNM.