[Study on the correlation between BRAF(V600E) mutation and lymphatic metastases in papillary thyroid cancer staged preoperativelv as N0].

Objective: To study the prevalence of BRAF(V600E) mutations in small (≤ 2 cm) papillary thyroid carcinoma (PTC), explore the correlation with occult central nodal metastasis (CNM) of clinically-nodal negative (cN0) neck for small (≤ 2 cm) papillary thyroid carcinoma (PTC).

Method: Primary tumor tissue (paraffin-embedded) from 72 patients with small (≤ 2 cm) cN0 PTC who underwent prophylactic central neck dissection (pCND) was tested for BRAF mutation. by nested PCR, the factors of lymph node metastasis such as clinicopathologic including tumor size, multifocality, extrathyroidal invasion, and BRAF mutations were analyzed. Prediction scores were generated using logistic regression models and BRAF was evaluated to see if it was a risk factor for CNM.

Result: The prevalence of BRAF was 47.22% (34/72) while the rate of CNM was 36.11% (26/72). Univariate analysis showed that the risk factors of lymph node metastasis for cN0 PTC were significantly correlated with tumor size (P = 0.016), bilateral tumor (P = 0.010), multifocality (P = 0.026), extrathyroidal invasion (P = 0.024), and BRAF mutations (P = 0.041). Univariate analysis showed that tumor size (OR = 2.674, 95% CI = 1.702-3.997), multifocality (OR = 1.371, 95% CI = 1.065-2.087), extrathyroidal invasion (OR = 0.540, 95% CI = 0.396-0.794) and BRAF (OR = 1.647, 95% CI = 1.101-2.463) were risk predictors of CNM.

Conclusion: The incidence of central neck micrometastatic disease is 36.11% in patients with PTC deemed N0 preoperatively by clinical examination and ultrasound of the neck lymph nodes and intraoperatively by inspection of the central compartment. The factors of high risk of CNM included tumor size, multifocality, extrathyroidal invasion, BRAF mutations. When a patient has the risk factors of lymph node metastasis should be electived prophylactic CCND.