Aim: To investigate the clinical effects of MUC1  on papillary thyroid cancer (PTC) and explore the relationship between MUC1  expression and BRAF  mutation. 
Methods: The data of 69 patients subjected to fine-needle aspiration biopsy in our hospital and 486 patient data downloaded from The Cancer Genome Atlas (TCGA) database were used. Univariate and multivariate analyses were performed.
Results: The results on the 486 patients recorded in the TCGA indicated that high MUC1  expression was independently related to BRAF  mutation, lymph node metastasis (LNM), and unifocal type. In the 69 fine-needle aspiration biopsy patients with PTC, high MUC1  expression was significantly related to LNM and extrathyroid extension (ETE). The result of Pearson’s correlation coefficient showed that BRAF  mutation and MUC1  expression were moderately correlated. Moreover, in the subgroup with low MUC1  expression, the patients with BRAF  mutation had higher ETE frequency and LNM than those without BRAF  mutation. In the subgroup with BRAF  mutation, patients with high MUC1  expression exhibited higher ETE frequency than those with low MUC1  expression, and high MUC1  expression occurred in older patients. In the subgroup with BRAF  wild-type mutation, patients with high MUC1  expression had a higher incidence of ETE and LNM than those with low expression.
Conclusion: We demonstrated that the MUC1  is an important oncogene in PTC and may have great significance on therapeutic cancer vaccine development.
Keywords: MUC1 , BRAF  mutation, papillary thyroid cancer, prognosis, lymph node metastasis, extrathyroid extension