Background and Aim: Thyroid papillary carcinoma (PTC) is the most common thyroid cancer. BAX gene is the first known pro-apoptotic member of the Bcl-2 protein family. The aim of this study was to investigate the relationship between BAX expression and some prognostic factors in PTC and papillary microcarcinoma (PMC).

Materials and Methods: In this cross-sectional, descriptive – analytical study, we obtained data from the records of 105 patients who had undergone thyroidectomy with a final diagnosis PMC and PTC, in Mostafa-Khomeini Hospital, from 2012 to 2014. The data included age, gender, tumor size and lymph node involvement. We investigated BAX expression by immunohistochemistry staining and capsular invasion by hematoxylin – eosin staining. Considering the percentage of positive tumor cells, BAX grading was done. Data were analyzed by Fischer's ،Chi-Square and T tests.

Result: In this study, 87.5% of patients were female. 81.9 % of patients had no lymph node involvement. There was only a significant association between the type of tumor and lymph node involvement (P= 0.02). We found no significant difference between papillary and micropapillary carcinoma in regard to BAX expression. Different grades of BAX expression had significant relationship with tumor size, lymph node involvement, and capsular invasion (P<0.001). Age (P˂0.02), BAX gene expression (P=0.001) and tumor size (P˂0.001) showed significant statistical relationships with one another.

Conclusion:  BAX expression is associated with lymph node involvement, capsular invasion and mean tumor size; and can be used to estimate the prognosis of PMC and PTC.

Keywords: Papillary thyroid carcinoma, Prognosis, BAX.

Received: Jun 25, 2016      Accepted: Dec 21, 2016