[Microsatellite instability in patients with diagnostic of colorectal cancer].

Objective: To determine the presence of microsatellite instability in patients with colorectal cancer using the molecular panel Bethesda and discuss its significance in patients with suspected hereditary nonpolyposis colorectal cancer (HNPCC) or Lynch Syndrome.
Materials and Methods: We worked with samples of peripheral blood and tumor tissue of 28 patients diagnosed with colorectal cancer referred to the Laboratory of Molecular Biology of the Instituto Nacional de Enfermedades Neoplasicas (INEN), Lima, with suspected of Lynch syndrome. DNA was extracted using kits of nucleic acid extraction of peripheral blood and paraffin-embedded tumor tissue. Five microsatellite markers of Bethesda panel were amplified: BAT25, BAT26, D2S123, D5S346 and D17S250, by polymerase chain reaction. IMS analysis was performed by electrophoresis on chip in the Bioanalyzer Agilent 2100.
Results: Of the patients studied, 11 had high IMS(IMS-H) and one could not be fully ranked, staying as MSI-H / IMS-L. In all cases of IMS-H both BAT26 and BAT25 were unstable. The IMS-H in these patients indicates high probability of HNPCC or Lynch syndrome; it must be contrasted with the genetic analysis of MMR genes.
Conclusion: The technique allowed determine which patients have to continue with the study of system mismatch repair genes, for establish whether we facing to HNPCC or sporadic colorectal cancer.