Clinical implications of Delphian lymph node metastasis in papillary thyroid carcinoma

Background: As is known, identifying risk factors precisely for lymph node metastasis (LNM) plays a vital role in initial treatment for papillary thyroid carcinoma (PTC). Nonetheless, whether Delphian lymph node (DLN) metastasis has value in predicting LNM remains an open question. This study covered a sample of 1,575 patients, which is the largest sample group so far, aiming to assess the predictive validity of DLN metastasis in PTC. Method: This retrospective cohort study was conducted with 1,575 eligible PTC patients who underwent thyroid operation between July 2013 and December 2018 and dinicopathologic parameters of patients with DLN metastasis were compared with those without DLN metastasis. Results: The incidence of DLN metastasis, according to our research samples, is 24.4% (384/1,575 patients). And results show that DLN positivity was closely associated with adverse prognostic factors including younger age, larger tumor size, extrathyroid extension, tumor location in the isthmus or upper lobe of the thyroid, number of LNM >5, higher recurrence. After carefully adjusting important confounding factors, we find that in multivariate logistic regression analyses, DLN metastasis is an independent predictor for both central LNM (CLNM, adjusted OR =7.81, P<0.001) and lateral LNM (LLNM, adjusted OR =3.40, P<0.001). Moreover, the stratified analyses also show convincing evidence of a positive correlation between DLN metastasis and LNM in levels II-IV in the vast majority of subgroups. Conclusions: The present study suggests that DLN metastasis is an independent risk factor for CLNM and LLNM of levels II-IV. The cervical lymph nodes should be meticulously evaluated to guide tailored treatment during operation in patients with DLN involvement.