Somatic mutations of MMR gene are not often present in HNPCC and in sporadic RER+ colorectal cancers. Complete studies were made according to Bethesda and Amsterdam Criteria, and 35 patients belonged to the group with sporadic colorectal cancer, and 9 patients belonged to HNPCC group. The results of our studies showed that there is no significant difference between RER phenotype of HNPCC and sporadic cancer (p>0,05) in regard to microsatellite status. It can be a good indicator that there are so called 'susspected' on HNPCC among sporadic cancers which were not detected yet. The reason for this was an incomplete familial history of illness of patients and as such it was selected as sporadic cancer. Microsatellite analysis together with medical and familial history of illness can be a successful instrument for efficient HNPCC identification. However, successful solving of this problem lies in making an accurate diagnosis in comparative findings, which can be provided by genetic and clinical tests.

Colorectal cancer with its frequency, high mortality rate as well as many etiological unknowns is a challenge to contemporary science. Finally, genetic information could be used in near future for prevention of colorectal cancer, its early diagnosis and selection for the most suitable hospital treatment. In this study, we analysed genetic alterations of tumor suppressor genes and the possibility of quick and efficient screening method for identification of colorectal cancer. The study consisted of 54 samples of tumor and surrounding healthy tissue of patients with colorectal cancer, which is clasificated according to Bethesda and Amsterdams criterias. The investigation showed that genetic alterations of tumor suppressor gene NM 23 were present in 19/35 (54,29%) samples, and tumor suppressor gene p53 in 18/35 (51,43%), APC in 18/35 (51,43%), DCC2 tumor suppressor gene in 12/35 (34,29%), tumor suppressor gene RB1 in 8 /35 (22, 86%) and DCC 1 in 10/35 ( 28,57%) tumor tissue.

HNPCC (Hereditary non-polyposis colorectal cancers) development is caused by mutation of genes included in system of mismatch repair genes. The mutation exists at 60% of patients in hMSH2 gene, 30% in hMLH1 and 10% both in hPMS1and hPMS2 genes. RER+ exists in about 90% in hereditary non-polyposis colorectal cancer and about 15-28% in sporadic cancers. The purpose of the study was to determine highly sensitive microsatellite markers which can be fast and efficient way of microsatellite screening for detection of HNPCC patients. Moreover, we have analysed the loss of heterozygosity of tumour suppressor genes which could have the diagnostic value in detection of HPNCC patients.