Comprehensive evaluation of risk factors for lymph node metastasis with papillary thyroid carcinoma in Southwest China patients

Background: With the increasing incidences of papillary thyroid cancer(PTC), it is important to risk-stratify patients who may have more aggressive tumor biology. This study aimed to evaluate the risk factors for lymph node metastasis with PTC in Southwest China Patients which may provide a substantial reference for clinical diagnosis and treatment. Methods: 1045 PTCs (313 PTMC and 732 non-PTMC) between August 2016 and August 2019 were examined totally (including one Tibetan). BRAF V600E mutation was tested in all samples. The clinical data (gender, age, tumor location, sample source and pathological features) were retrospectively analyzed. Logistic regression analysis was performed to evaluate independent risk factors for LNM. Results: 181 out of 313 PTMC cases (57.8%), 145 out of 732 non-PTMC cases (19.8%) had BRAF V600E mutation, the Tibetan had a double mutation of BRAF L597Q and V600E in two separate lesions. In PTMC, significant difference in gender and sample source was found (BRAF V600E mutation vs. wild-type). In non-PTMC, significant difference in gender was found (BRAF V600E mutation vs. wild-type). The female (OR=1.952; 95% CI= 1.373-2.774; P= 0.00), age (31-59 years) and diameter of tumor ≤1cm (OR=3.273; 95% CI= 2.417-4.432; P=0.000) were significant independent predictors of LNM in all PTCs. In PTMC, the female (OR= 3.002; 95% CI= 1.654-5.446; P= 0.00) was a significant independent predictor of LNM. The tumor in left and right lobes simultaneously was an independent protective factor of LNM in each group (PTCs: OR=0.287; PTMC: OR=0.170; non-PTMC: OR=0.441, respectively). The BRAF V600E mutation rate of US-FNAC was much higher than FFPE in PTMC (P=0.018). Conclusions: Unlike previous research, our findings suggested that the female patients and diameter of tumor ≤1cm were risk factors for LNM and the BRAF V600E wild-type of PTMC might be more aggressive than others. Interestingly, the position of tumor in bilateral thyroid simultaneously was an independent protective factor for LNM. The US-FNA should be recommended for gene analysis (BRAF V600E) in PTMC. The BRAF L597Q mutation may be an independent aggressive factor in the Chinese Tibetan population. Hence, clinicians should consider an individualized treatment according to gene mutation, gender, age, tumor size and location of tumor in order to achieve a better therapeutic efficacy.