The occurrence of and predictive factors for multifocality and bilaterality in patients with papillary thyroid microcarcinoma

Thyroidectomy or hemithyroidectomy may be performed as treatment for papillary thyroid microcarcinoma (PTMC). However, in cases of bilateral PTMCs, only thyroidectomies should be recommended. Sometimes bilateral PTMC may be undetected in presurgical evaluations, so reoperation might be necessary after a partial thyroid resection. The aim of this study was to assess the occurrence of and predictive factors for the multifocality and bilaterality of PTMCs. We performed a retrospective review of 4716 consecutive patients with thyroid tumors. Of these patients, 434 (9.2%) had thyroid malignancies. All patients underwent thyroidectomies with central and/or lateral lymph node dissection between January 2008 and December 2017. PTMC was identified in 177 (3.75%) individuals. Solitary PTMC was observed in 114 (64.4%) patients, multifocal PTMC was seen in 48 (27.1%) patients, and bilateral PTMC was detected in 15 (8.5%) patients. The occurrence of solitary PTMC increased from 11.1% in 2008 to 61.9% in 2017. The occurrence of multifocal tumors significantly decreased from 77.8% in 2008 to 6.3% to 18.4% in 2013 to 2016 (P < .05). The occurrence of bilateral tumors, with respect to all PTMC cases, did not change during the 10-year period. We observed significantly higher rates of hypoechogenicity, more microcalcifications, more irregular margins, larger tumor sizes, and higher vascularity in the patients with multifocal and bilateral tumors than in the patients with solitary tumors (P < .0001 for all). The occurrence of bilateral PTMC is not very common. In patients with PTMC, thyroidectomy should be considered when microcalcifications, an irregular tumor shape, unclear margins, hypoechogenicity, high vascularity, and a large tumor size are observed. These clinicopathological features are prognostic factors for multifocal and bilateral PTMC.