Malignant thyroid lesions are the most common
malignancy of the endocrine glands with increasing rates in the last two decades.
Papillary thyroid cancer is the most common thyroid
malignancy. In our study, we aimed to quantitatively evaluate the levels of DNA repair
proteins MSH2, MLH1, MGMT, which are representative blocks of patients diagnosed with
papillary carcinoma,
chronic thyroiditis, or colloidal
goiter. Total or subtotal
thyroidectomy material of 90 patients diagnosed with
papillary carcinoma, nodular colloidal
goiter, or
chronic thyroiditis between 2009 and 2012 were retrospectively evaluated. Tissue samples obtained from
paraffin blocks were stained with MGMT, MSH2, MLH1
proteins and their immunohistochemistry was evaluated. Prepared sections were examined qualitatively by an impartial pathologist and a clinician, taking into account the staining method under the trinocular light microscope. Although there was no statistically significant difference in MGMT, MSH2, MLH1, follicular cell positivity, staining intensity, and immunoreactivity values,
papillary carcinoma cases showed a higher rate of follicular cell positivity, and this difference was more pronounced between
papillary carcinoma and colloidal
goiter. In the MSH2 follicular cell positivity evaluation, the difference between
chronic thyroiditis and colloidal
goiter was significant (p = 0.023). The difference between
chronic thyroiditis and colloidal
goiter was significant in the MSH2 staining intensity evaluation (p = 0.001). The difference between
chronic thyroiditis and colloidal
goiter was significant in MLH1 immunoreactivity evaluation (p = 0.012).
Papillary carcinoma cases were demonstrated by nuclear staining only for MSH2 and MLH1
proteins as opposed to hyperplastic nodules. The higher levels of expression of DNA repair genes in malignant
tumors compared to benign
tumors are attributed to the functional activation of DNA repair genes. Further studies are needed for DNA repair
proteins to be a potential test in the development and progression of
thyroid cancer.