Papillary thyroid microcarcinomas that metastasize to lymph nodes

We aimed to determine clinicopathological features that can predict lymph node metastasis (LNM) in papillary thyroid microcarcinomas (PTMC).

Medical records of 872 patients with papillary thyroid cancer >1 cm (PTC > 1 cm) and 1184 patients with papillary thyroid microcancer (PTMC) (≤1 cm) were reviewed retrospectively. Demographical, clinical and histopathological features of (PTC > 1 cm) and PTMC were compared. Association between clinicopathological features and LNM in PTMC was investigated.

The median age of patients with PTMC was significantly higher than patients with PTC > 1 cm (49 vs 46 years old, p < 0.001). Multifocality, capsular invasion, vascular invasion, extrathyroidal extension (ETE) and LNM were more frequent in patients with PTC > 1 cm compared to patients with PMTC (p < 0.001 for each). In PTMC group, those with LNM had significantly higher proportion of multifocality, capsular invasion, vascular invasion and ETE compared to those without LNM (p = 0.007, <0.001, p = 0.011 and p < 0.001, respectively). Multifocality and ETE were significant factors for LNM with logistic regression analysis. Multifocality increased the risk of LNM by 1.737 times (95% CI: 1.079-2.979) and ETE increased the risk by 3.528 times (95%: 1.914-6.503). Primary tumor diameter ≥ 5.75 mm was predictive for LNM with a sensitivity of 0.782 and a specificity of 0.517 in PTMC.

LNM should be investigated more carefully in patients with PTMC in the presence of tumor diameter ≥ 5.75 mm, multifocality or ETE.