Risk factors for lateral neck lymph node metastasis in papillary thyroid ultra micro carcinoma with implications for active surveillance.

Papillary thyroid ultra-microcarcinoma (PTUMC), defined as a tumor ≤ 0.5 cm in size, can be considered for active surveillance management. However, lateral neck node metastases also occur in patients with PTUMCs. This study evaluated the clinicopathological features of PTUMC and compare the clinicopathological characteristics of patients with PTUMC with and without lateral neck lymph node metastasis. The study included 3,004 patients with PTUMC treated between January 2009 and June 2013; of these, 89 (3.0%) had lateral neck node metastasis. Clinicopathological characteristics including sex, age, size, operation type, tumor location, multiplicity, thyroiditis, microscopic extrathyroidal extension (ETE), and nodal status were compared between the two groups. Patients with PTUMC presented with significant male sex (p = 0.014), microscopic ETE (p < 0.001), multiplicity (p < 0.001), upper pole lesions (p < 0.001), psammomatous calcification, and central node metastasis (p < 0.001). Multivariate analysis revealed microscopic ETE (p = 0.003), upper pole lesions (p < 0.001), psammomatous calcification (p = 0.002), central neck node metastases (p < 0.001) and aggressive subtype(p < 0.001) are independent risk factors for lateral neck metastasis in PTUMC, warranting careful consideration when deciding between active surveillance and surgical intervention in this patient population.