Endocrine Abstracts

Aims: Bening and malignant thyroid nodules are the most common lesions of endocrine glands. Some molecular markers; Mut-S homolog-2 (MSH2) and Mut-L-homolog-1 (MLH1) are the two of DNA repair proteins and metil guanin–DNA-metil transferase (MGMT) is the DNA repair enzymes have been studied. In this study, our aim is to evaluate MSH2, MLH1, and MGMT levels in papillary thyroid cancer (PTC), multinodular colloidal goitre (MNG), and chronic lymphocytic thyroiditis (CLT) and define as new diagnostic markers.

Materials and methods: Ninety patients’ tissue specimens obtained from total or subtotal thyroidectomy materials with PTC (n=29; 50.07±16.42 years), MNG (n=26; 52.96±17.09 years), and CLT (n=29; 46.21±11.80 years) were evaluated. The specimens were studied for MGMT, MSH2, and MLH1 immunohistochemically. Descriptive analysis, ANOVA test and Pearson’s χ² test were used for statistical analysis.

Findings: Despite all MGMT, MLH1, and MSH2 were similar for follicular cell expression statistically, the staining was noticible in PTC group. The expressions for MGMT and MSH2 were similar for staining density and immunoreactivity within groups, but the expressions were more pronounced in PTC cells with nuclear and cytoplasmic staining. The groups were reevaluated for MSH2 follicular cell expression as <50% and ≥50%. In this model CLT and MNG groups were different (P=0.023) and the difference was significant for staining density and immunreactivity (P=0.001 and P=0.044 respectively). Follicular cell expression between PTC and MNG (P=0.032), and immunoreactivity between CLT and MNG (P=0.012) were different for MLH1.

Results: Repair of DNA and the expression of its biomarkers are pronounced in malignant lesions. In this study, we found an increased expression of the three biomarkers MGMT, MLH1 and MSH2 in PTC compared to MNG as similar to CLT. Our result showing that these new biologic markers are useful differentiating benign and malignant lesions.