Nodal metastasis in well-differentiated follicular carcinoma of the thyroid: Its incidence and clinical significance.

The clinical significance of nodal metastasis in well-differentiated follicular carcinoma (WD-FC) of the thyroid remains a controversial issue. This study aimed to clarify clinical and pathological characteristics of WD-FC with nodal metastasis, based on the new WHO classification. We examined 249 WD-FC cases diagnosed between 1983 and 2004 in our hospital. Poorly differentiated follicular carcinoma was not included in this study. Of the 249 WD-FC cases, 9 (3.6%) revealed nodal metastasis. The incidences of nodal metastasis in minimally invasive and widely invasive cases were 2.0 and 9.8%, respectively. In four patients, nodal metastasis was detected in the ipsilateral lymph nodes during the initial surgery. A total of 6 patients presented with nodal metastasis 2-10 years after the initial operation, and 3 patients with bilateral and large nodal metastases were relatively young. No patients succumbed to the carcinoma. Primary lesions of WD-FC with nodal metastasis were microscopically conventional, and there were no findings predicting nodal metastasis. We hypothesized that the incidence of nodal metastasis in WD-FC, based on the new WHO classification, was lower compared with previous reports. Younger individuals may be at a higher risk of large bilateral nodal metastasis. The presence of nodal metastasis did not affect the long-term outcome of follicular carcinoma.