Breast and ovarian cancer predisposition due to de novo BRCA1 and BRCA2 mutations.

BRCA1 and BRCA2 are the two major genes predisposing to breast and ovarian cancer. Whereas high de novo mutation rates have been demonstrated for several genes, only 11 cases of de novo BRCA1/2 mutations have been reported to date and the BRCA1/2 de novo mutation rate remains unknown. The present study was designed to fill this gap based on a series of 12 805 consecutive unrelated patients diagnosed with breast and/or ovarian cancer who met the inclusion criteria for BRCA1/2 gene analysis according to French guidelines. BRCA1/2 mutations were detected in 1527 (12%) patients, and three BRCA1 mutations and one BRCA2 mutation were de novo. The BRCA1/2 de novo mutation rate was estimated to be 0.3% (0.1%; 0.7%). Although rare, it may be useful to take the possibility of de novo BRCA1/2 mutation into account in genetic counseling of relatives and to improve the understanding of complex family histories of breast and ovarian cancers.

Rare germline large rearrangements in the BRCA1/2 genes and eight candidate genes in 472 patients with breast cancer predisposition.

Hereditary breast cancers account for up to 5-10 % of breast cancers and a majority are related to the BRCA1 and BRCA2 genes. However, many families with breast cancer predisposition do not carry any known mutations for BRCA1 and BRCA2 genes. We explored the incidence of rare large rearrangements in the coding, noncoding and flanking regions of BRCA1/2 and in eight other candidate genes--CHEK2, BARD1, ATM, RAD50, RAD51, BRIP1, RAP80 and PALB2. A dedicated zoom-in CGH-array was applied to screen for rearrangements in 472 unrelated French individuals from breast-ovarian cancer families that were being followed in eight French oncogenetic laboratories. No new rearrangement was found neither in the genomic regions of BRCA1/2 nor in candidate genes, except for the CHEK2 and BARD1 genes. Three heterozygous deletions were detected in the 5' and 3' flanking regions of BRCA1. One large deletion introducing a frameshift was identified in the CHEK2 gene in two families and one heterozygous deletion was detected within an intron of BARD1. The study demonstrates the usefulness of CGH-array in routine genetic analysis and, aside from the CHEK2 rearrangements, indicates there is a very low incidence of large rearrangements in BRCA1/2 and in the other eight candidate genes in families already explored for BRCA1/2 mutations. Finally, next-generation sequencing should bring new information about point mutations in intronic and flanking regions and also medium size rearrangements.

Prenatal diagnosis of sacrococcygeal teratoma with constitutional partial monosomy 7q/trisomy 2p.

We report the prenatal diagnosis of a fetus with sacrococcygeal teratoma and facial dysmorphism attributed to a constitutional terminal deletion of chromosome 7q and partial trisomy of chromosome 2p likely resulting from a de novo balanced translocation. The cytogenetic abnormality was diagnosed prenatally after sonographic detection of teratoma and confirmed on peripheral blood cells at birth. The newborn died of post-operative complications at seven days of age. FISH analysis demonstrated haploinsufficiency of HLXB9, a gene identified in the triad of a presacral mass (teratoma or anterior meningocele), sacral agenesis, and anorectal malformation, which constitutes the Currarino syndrome. Despite the absence of other features of the triad, the teratoma observed in the fetus we describe might represent a partial form of Currarino syndrome.