The increasing incidence of papillary thyroid cancer, primarily papillary microcarcinoma, represents a significant diagnostic and therapeutic problem and a burden for patients and the health care system. Although papillary carcinomas are considered to be cancers of low mortality, they carry a significant risk of regional spread of disease, which consequently leads to increased morbidity, given that the primary method of treatment is surgery. Currently, there are no biomarkers that could, preoperatively, with high specificity and sensitivity, differentiate an indolent disease from a more aggressive one. Such preoperative differentiation would enable optimal treatment planning with a significant reduction in burden and morbidity of the treatment itself. According to all currently accepted classifications, papillary microcarcinomas belong to the group of low-risk papillary carcinomas, but they are still significantly prone to regional spread of disease. In this thesis, the proteomic profile of 30 papillary microcarcinomas was analyzed – 15 that did not metastasize at the time of surgical treatment and 15 that metastasized to the lateral regions of the neck. The proteomic profile of papillary microcarcinomas showed a significant difference in protein and gene expression, depending on the observed group. In the group with metastases, certain proteins were identified that could lead to metastatic disease and more aggressive biological behavior. These are ubiquitin conjugating enzyme E2 variant 1, sodium- and chlorine-dependent taurine transporter, syndecans -2 and -4, alpha-1-antirypsin, histone-lysine N-methyltransferase 2C and citrate synthase. Increased expression of three genes, PLAU, ATF1 and CREB1, was also identified in the group with metastases, which could also potentially play a role in the more aggressive behavior of certain papillary microcarcinomas. Considering the results and the fact that, to our knowledge, this is the first proteomic thesis that compared papillary microcarcinomas that gave regional metastases and those that did not, this thesis brought new knowledge about protein expression and the potential pathophysiological role of differentially expressed proteins in papillary thyroid microcarcinomas and laid the foundations for future research.