Association between TNM staging system and histopathological features in patients with papillary thyroid carcinoma

We aimed to assess the validity of the American Joint Committee on Cancer (AJCC) tumor-node-metastasis (TNM) staging system in patients with papillary thyroid carcinoma (PTC) by evaluating the relationships between clinicopathologic factors and TNM stage using histopathological specimens and electronic medical records. We enrolled 733 consecutive patients who had undergone thyroid surgery for PTC between 2010 and 2013. Clinical data were obtained from electronic medical records. TNM stages, multifocality, and bilaterality were analyzed after review of histopathological specimens by applying the AJCC TNM staging system. Multiple statistical analyses were performed to evaluate the correlation between the AJCC TNM staging system and the clinicopathologic factors. Of the 733 patients, there were T stage including T1a (46.9 %, 344/733), T1b (12.6 %, 92/733), T2 (2.0 %, 15/733), T3 (38.1 %, 279/733), T4a (0.4 %, 3/733), and T4b (0 %, 0/733), N stage including N0 (58.9 %, 432/733), N1a (24.3 %, 178/733), and N1b (16.8 %, 123/733), and multiplicity including multifocality (31.1 %, 228/733) and bilaterality (23.7 %, 174/733). There was a significant association between the PTC primary tumor size and T stage, N stage, multifocality, and bilaterality (p < 0.0001). Multifocality, bilaterality, and the presence of nodal metastasis were most frequently seen in patients with T3 stage (p < 0.0001). In multivariate logistic regression analyses, T and N stages were independent predictors of multiple PTCs. The PTC primary tumor size had a significant association with the T and N stages of the AJCC TNM staging system, and these factors were independent predictors of multifocality and bilaterality.