2012 年 59 巻 2 号 p. 119-125
It is well-known that papillary thyroid carcinoma (PTC) has a generally indolent character and shows a favorable prognosis unless it has no high-risk features such as clinical lymph node metastasis, distant metastasis, and significant extrathyroid extension. In this study, we investigated the prognosis of 3,965 patients with PTC without these features. We classified these patients into 3 groups: T-1, tumor ≤ 2 cm (n = 2,591); T-2, tumor 2.1-4 cm (n = 1,123); T-3, tumor > 4 cm (n = 251). Ten-year recurrence rates of T-1, T-2, and T-3 patients were 0.3, 1.3, and 1.9% for the thyroid (in the subset of patients who underwent limited thyroidectomy), 1.9, 4.6, and 8.1% for lymph nodes, and 0.4, 1.6, and 3.4% for distant organs, respectively. A tumor size larger than 2 cm had an independent prognostic impact on all these recurrences also on multivariate analysis. These findings suggest that PTC larger than 2 cm exhibited more aggressive biological characteristics than that measuring 2 cm or less, even though it had no other high-risk features. However, the incidences of distant recurrence and carcinoma death were still low and it remains unclear whether extensive surgery is mandatory for otherwise low-risk PTC patients with large tumor.