Genealogical tree study as screening method in the Lynch syndrome prior to genetic test.

Objectives: Despite genetic advances in the study of Lynch syndrome (LS), difficulties remain in the diagnosis of the syndrome. The aim of this study was to assess the usefulness of a detailed genealogical tree as a screening method to identify Tenerife island families with a high probability of LS.

Methods: We elaborated complete genealogical trees of the families. According to the degree of fulfillment of the Amsterdam Criteria II, the genealogical trees were classified as high or low probability of LS. Additionally, we analyzed the level of tumor microsatellite instability (MSI+) and identified a mutation in exon 13 of the MSH2 gene by single-strand conformation polymorphism, sequencing, and PCR-RFLP.

Results: According the genealogical trees, we found 10 families with high probability of LS and 30 families with low probability of LS. The families with high probability of LS showed high MSI+ in all cases. Conversely, families with low probability were MSS (microsatellite stable). In 5 of the 10 families with high probability, we discovered a T-->G mutation in position 688 of exon 13 of MSH2, which appeared in all the family members with the tumor, except 1 patient with a retinoblastoma.

Conclusions: Our results indicate that genealogical tree is a highly effective tool for classifying families with a high probability of Lynch Syndrome prior to genetic test.