Comparison of prognosis according to tumor size in papillary thyroid carcinoma with lateral cervical node metastasis

Background: Lateral lymph node metastasis (LNM), which significantly impacts papillary thyroid carcinoma (PTC) patients’ prognosis, occurs not uncommonly in papillary thyroid microcarcinoma (PTMC). PTMC is known to have a much better prognosis than non-PTMC, but it has not been known whether there is such a difference even with lateral LNM. Methods: This retrospective study included a series of 3336 consecutive PTC patients who underwent thyroidectomy. Of them, 206 had lateral LNM and were divided into the PTMC and non-PTMC groups by tumor size (1-cm) for comparing the prevalence of prognostic factors. Results: LNM was in 157/1131 (13.9%) non-PTMC patients and 49/2205 (2.2%) PTMC patients. Eleven of the 206 (5.3%) lateral LNM cases not found on US were only seen on computed tomography. The prevalence of prognostic factors which include an age of >55 years, >5 metastatic lymph nodes (LNs), high metastatic-to-examined LN ratio, and large metastatic LNs (>3 cm) were not significantly different between PTMC and non PTMC group. Conclusions: In PTC with lateral LNM, the prognosis is likely to be similar regardless of tumor size. Considering the modest risk of lateral LNM in PTMC, FNA and detailed radiologic for small tumor should be encouraged.