RESUMEN
Lynch syndrome is an autosomal dominant cancer predisposition syndrome caused by germline mutations in one of the mismatch repair (MMR) genes: MLH1, MSH2, MSH6 and PMS2. Clinically, Lynch syndrome is characterized by early onset (45 years) of colorectal cancer (CRC), as well as extra-colonic cancer. Male and female carriers of Lynch syndrome-associated mutations have different lifetime risks for CRC and in women endometrial cancer (EC) may be the most common tumor. Whenever Amsterdam criteria are not fulfilled, the currently recommended laboratory screening strategies involve microsatellite instability testing and immunohistochemistry staining of the tumor for the major MMR proteins. The aim of this study was to estimate the frequency of MMR deficiencies in women diagnosed with EC who are at-risk for Lynch syndrome. Thirty women diagnosed with EC under the age of 50 years and/or women with EC and a first degree relative diagnosed with a Lynch syndrome-associated tumor were included. To assess MMR deficiencies four methods were used: multiplex PCR, Single Strand Conformation Polymorphism, Immunohistochemistry and Methylation Specific-Multiplex Ligation-dependent Probe Amplification. Twelve (40%) patients with EC fulfilling one of the inclusion criteria had results indicative of MMR deficiency. The identification of 5 women with clear evidence of MMR deficiency and absence of either Amsterdam or Bethesda criteria among 10 diagnosed with EC under the age of 50 years reinforces previous suggestions by some authors that these women should be considered at risk and always screened for Lynch syndrome after informed consent.