Neutrophil-to-Lymphocyte Ratio Is Associated With the Proportion of Poorly Differentiated Components in Papillary Thyroid Carcinoma

Introduction Diagnosis of poorly differentiated thyroid cancer (PDTC) requires ≥ 50% of poorly differentiated components (PDC) in Japan. However, the optimal cutoff percentage of PDC for PDTC diagnosis remains controversial. Although high neutrophil-to-lymphocyte ratio (NLR) correlates with the aggressiveness of papillary thyroid cancer (PTC), whether NLR is associated with the proportion of PDC in PTC remains unstudied. Materials and methods Patients with the pure PTC (n = 664), PTC with < 50% PDC (n = 19), or PTC with ≥ 50% PDC (n = 26) who underwent surgery were retrospectively analyzed. Twelve-year disease-specific survival and preoperative NLR were compared among these groups. Results Twenty seven patients died from thyroid cancer. The PTC with ≥ 50% PDC group (80.7%) showed significantly worse 12-year disease-specific survival than the pure PTC group (97.2%) (P < 0.001); however, the < 50% PDC group (94.7%) did not (P = 0.91). The PTC with ≥ 50% PDC group had a significantly higher NLR than the pure PTC (P < 0.001) and the PTC with < 50% PDC groups (P < 0.001), whereas there was no significant difference in the NLR between the pure PTC and the PTC with < 50% PDC groups (P = 0.48). Conclusions PTC with ≥ 50% PDC is more aggressive than either pure PTC or PTC with < 50% PDC, and NLR potentially reflects the PDC proportion. These results support the validity of 50% PDC as a cut-off for PDTC diagnosis and indicate the utility of NLR as a biomarker for PDC proportion.