Bilateral versus unilateral papillary thyroid microcarcinoma: predictive factors and associated histopathological findings following total thyroidectomy

OBJECTIVE: The extent of thyroidectomy for papillary thyroid microcarcinoma (PTMC) is debatable. This study investigated the rate and predictive factors of bilateral versus unilateral PTMC with the objective of identifying those patients who may benefit from total thyroidectomy. DESIGN: Between January 2001 and December 2008, 2019 patients who underwent total thyroidectomy were examined. A total of 319 patients diagnosed histopathologically as PTMC were included in the study. The predictive value of age at diagnosis, gender, tumor size, multifocality, lymph node metastasis, thyroid capsule invasion and nonincidental diagnosis using univariate and multivariate analyses were retrospectively analyzed. RESULTS: Of the 319 patients with PTMC, 77 (24.1%) presented bilateral disease. In univariate analysis, size of tumor >= 5mm (p<0.001), multifocality (p<0.001), lymph node metastases (p<0.001), thyroid capsule invasion (p<0.001) and nonincidental diagnosis (p=0.002) were significantly associated with bilaterality. In multivariate analysis, tumor size (p<0.001), multifocality of the primary tumor in the unilateral lobe (p<0.001) and lymph node metastasis (p<0.001) were independent predictive factors for bilateral PTMC. CONCLUSIONS: Tumor size >= 5mm and multifocality of the primary carcinoma in the unilateral lobe were independent risk factors for bilateral PTMC. Total thyroidectomy should be considered for these patients, which is of importance for the prediction of possible recurrence of disease.