A low proportion of BRCA2 mutations in Finnish breast cancer families.

Abstract One hundred breast cancer families were identified at the Helsinki University Central Hospital in Finland and were screened for germ-line mutations in the coding regions and splice boundaries of the BRCA2 gene. Eight families (8%) were found to carry five different mutations, all of which are predicted to prematurely truncate the protein product. These BRCA2 families have early-onset breast cancer (mean and median age = 49 years), with four of the eight families including ovarian cancer but with no families including male breast cancer. A wide spectrum of other cancers also is seen in these families. Three mutations were identified in more than one family, and haplotype analysis in the families suggested a common founder for each recurrent mutation. One recurrent mutation, 999del5, previously has been noted as a common mutation in Iceland. The relationship between the Icelandic 999del5 mutation and the Finnish 999del5 mutation was explored by comparison of families from both countries. A common haplotype covering a minimal region intragenic to the BRCA2 gene was shared between the Icelandic and the Finnish mutation carriers.