Matrix Metalloproteinase-9 and the Cu/Zn Ratio as Ancillary Diagnostic Tools in Distinguishing Between the Classical and Follicular Variants of Papillary Thyroid Carcinoma

The most common histological variants of papillary thyroid carcinoma (PTC), classical (CPTC) and follicular (FPTC), have different diagnostic features, molecular biology, and prognosis. Matrix metalloproteinase-9 (MMP-9) endopeptidase which degrades the components of the extracellular matrix is essential in the invasive growth and metastasizing of malignant tumors. The serum copper (Cu)/zinc (Zn) ratios are sensitive diagnostic and prognostic indicators in oncology since Cu- and Zn-dependent enzymes play important roles in the genesis and the progression of tumors. The aim of this study was to examine the expressions of MMP-9 in tissues of CPTC and FPTC, as well as to determine the Cu/Zn ratios in the same samples. MMP-9 was determined immunohistochemically, and the concentrations of copper and zinc in thyroid tissue were determined by means of flame atomic absorption spectrometry. The results obtained revealed significantly higher expressions of MMP-9 in CPTC in comparison with FPTC, as well as higher Cu/Zn ratios in CPTC than in FPTC. Thus, determining MMP-9 activities and the Cu/Zn ratios could improve the accuracy of the standard histopathological diagnosis of these two types of PTC.