De novo BRCA1 mutation in a patient with breast cancer and an inherited BRCA2 mutation

A de novo germline pathogenic BRCA1 variant identified following an osteosarcoma pangenomic molecular analysis

De novo germline pathogenic variants (gPV) of the BReast CAncer 1 (BRCA1) gene are very rare. Only a few have been described up to date, usually in patients with a history of ovarian or breast cancer. Here, we report the first case of an incidental de novo BRCA1 germline pathogenic variant which was identified within the framework of the Plan France Médecine Génomique (PFMG) 2025 French national tumor sequencing program. The proband was a 29-year-old man diagnosed with metastatic osteosarcoma. Tumor whole exome sequencing identified a BRCA1 c.3756_3759del p.(Ser1253Argfs*10) pathogenic variant without loss-of-heterozygosity. A low genomic instability score and the absence of single base substitution signatures of homologous recombination deficiency suggested that the BRCA1 variant was not driver in the osteosarcoma tumorigenesis. Germline whole genome sequencing asserted the germline nature of this variant, with a 36% allele frequency, suggesting a mosaicism caused by a post-zygotic mutational event. The proband's family (parents and siblings) were not carriers of this variant confirming the de novo occurrence. Tumor sequencing programs like the French PFMG 2025 have been implemented worldwide and may help identify new gPV, including de novo variants.

A New de novo BRCA1 Mutation in a Young Breast Cancer Patient: A Case Report

Background

BRCA1 and BRCA2 genes represent the most investigated breast and ovarian cancer predisposition genes. Ten cases of pathogenic de novo BRCA1 variations and six cases of pathogenic de novo BRCA2 variation have been reported at present. Here, we report a new case of a de novo BRCA1 gene mutation.

Case Presentation

A 30-year-old woman with no health issues and no family history for hereditary breast and ovarian cancer was diagnosed with a hormone receptor positive/HER2 negative invasive breast cancer. Genetic testing revealed a pathogenic variant in BRCA1 (c.4065_4068delTCAA) which was not found in her parents or sister.

Conclusion

We report a new case of de novo BRCA1 mutation, confirmed by repeated germline testing of the index patient and her parents. The published BRCA1/2 de novo mutation rate is low. This is probably due - in part - to the strict testing criteria.

Five Italian Families with Two Mutations in BRCA Genes

Double heterozygosity (DH) in BRCA1 and BRCA2 genes and double mutation (DM) in BRCA1 or BRCA2 are extremely rare events in the general population, and few cases have been reported worldwide so far. Here, we describe five probands, all women, with breast and/or ovarian cancer and their families. Particularly, we identified two probands with DH in the BRCA1/2 genes with a frequency of 0.3% and three probands with DM in the BRCA2 gene with a frequency of 0.5%. The DH BRCA1 c.547+2T>A (IVS8+2T>A)/BRCA2 c.2830A>T (p.Lys944Ter) and BRCA1 c.3752_3755GTCT (p.Ser1253fs)/BRCA2 c.425+2T>C (IVS4+2T>C) have not been described together so far. The DM in BRCA2, c.631G>A (p.Val211Ile) and c.7008-2A>T (IVS13-2A>T), found in three unrelated probands, was previously reported in further unrelated patients. Due to its peculiarity, it is likely that both pathogenic variants descend from a common ancestor and, therefore, are founder mutations. Interestingly, analyzing the tumor types occurring in DH and DM families, we observed ovarian cancer only in DH families, probably due to the presence in DH patients of BRCA1 pathogenic variants, which predispose one more to ovarian cancer onset. Furthermore, male breast cancer and pancreatic cancer ensued in families with DM but not with DH. These data confirm that BRCA2 pathogenic variants have greater penetrance to develop breast cancer in men and are associated with an increased risk of pancreatic cancer.

Double Heterozygosity for BRCA1 Pathogenic Variant and BRCA2 Polymorphic Stop Codon K3326X: A Case Report in a Southern Italian Family

Here, we describe a patient with bilateral breast cancer and melanoma, and with a concomitant double variant, namely p.Gln563Ter in BRCA1 and p.Lys3326Ter in BRCA2. The BRCA2 p.Lys3326Ter (K3326X) (rs11571833) mutation identified in our patient is a debated substitution of thymidine for adenine which is currently regarded as benign polymorphism in main gene databases. Recent studies, however, describe this variant as associated with breast and ovarian tumors. Based on the observation of the cancer’s earliest age of onset in this subject, our purpose was to reevaluate this variant according to recent papers indicating a role of powerful modifier of the genetic penetrance. Genetic testing was performed in all consenting patient’s relatives, and in the collection of the clinical data particular attention was paid to the age of onset of the neoplasia. Following our observation that the our patient with double heterozygosis had an early age of onset for cancer similar to a few rare cases of double mutation for BRCA1 and BRCA2, we also performed an extensive review of the literature relative to patients carrying a double heterozygosity for both genes. In line with previous studies relative to the rare double heterozygosity in both BRCA1/2 genes, we found the earlier onset of breast cancer in our patient with both BRCA1/2 mutations with respect to other relatives carrying the single BRCA1 mutation. The presence of the second K3326X variant in our case induces a phenotype characterized by early onset of the neoplasia in a manner similar to the other cases of double heterozygosity previously described. Therefore, we suggest that during the genetic counseling, it should be recommendable to evaluate the presence of the K3326X variant in association with other pathogenic mutations.

Revertant mosaicism for family mutations is not observed in BRCA1/2 phenocopies

In BRCA1/2 families, early-onset breast cancer (BrCa) cases may be also observed among non-carrier relatives. These women are considered phenocopies and raise difficult counselling issues concerning the selection of the index case and the residual risks estimate in negative family members. Few studies investigated the presence of potential genetic susceptibility factors in phenocopies, mainly focussing on BrCa-associated single-nucleotide polymorphisms. We hypothesized that, as for other Mendelian diseases, a revertant somatic mosaicism, resulting from spontaneous correction of a pathogenic mutation, might occur also in BRCA pedigrees. A putative low-level mosaicism in phenocopies, which has never been investigated, might be the causal factor undetected by standard diagnostic testing. We selected 16 non-carriers BrCa-affected from 15 BRCA1/2 families, and investigated the presence of mosaicism through MALDI-TOF mass spectrometry. The analyses were performed on available tumour samples (7 cases), blood leukocytes, buccal mucosa and urine samples (2 cases) or on blood only (7 cases). In one family (n.8), real-time PCR was also performed to analyse the phenocopy and her healthy parents. On the 16 phenocopies we did not detect the family mutations neither in the tumour, expected to display the highest mutation frequency, nor in the other analysed tissues. In family 8, all the genotyping assays did not detect mosaicism in the phenocopy or her healthy parents, supporting the hypothesis of a de novo occurrence of the BRCA2 mutation identified in the proband. These results suggest that somatic mosaicism is not likely to be a common phenomenon in BRCA1/2 families. As our families fulfilled high-risk selection criteria, other genetic factors might be responsible for most of these cases and have a significant impact on risk assessment in BRCA1/2 families. Finally, we found a de novo BRCA2 mutation, suggesting that, although rare, this event should be taken into account in the evaluation of high-risk families.

Inheritance of deleterious mutations at both BRCA1 and BRCA2 in an international sample of 32,295 women

BACKGROUND

Most BRCA1 or BRCA2 mutation carriers have inherited a single (heterozygous) mutation. Transheterozygotes (TH) who have inherited deleterious mutations in both BRCA1 and BRCA2 are rare, and the consequences of transheterozygosity are poorly understood.

METHODS

From 32,295 female BRCA1/2 mutation carriers, we identified 93 TH (0.3 %). "Cases" were defined as TH, and "controls" were single mutations at BRCA1 (SH1) or BRCA2 (SH2). Matched SH1 "controls" carried a BRCA1 mutation found in the TH "case". Matched SH2 "controls" carried a BRCA2 mutation found in the TH "case". After matching the TH carriers with SH1 or SH2, 91 TH were matched to 9316 SH1, and 89 TH were matched to 3370 SH2.

RESULTS

The majority of TH (45.2 %) involved the three common Jewish mutations. TH were more likely than SH1 and SH2 women to have been ever diagnosed with breast cancer (BC; p = 0.002). TH were more likely to be diagnosed with ovarian cancer (OC) than SH2 (p = 0.017), but not SH1. Age at BC diagnosis was the same in TH vs. SH1 (p = 0.231), but was on average 4.5 years younger in TH than in SH2 (p < 0.001). BC in TH was more likely to be estrogen receptor (ER) positive (p = 0.010) or progesterone receptor (PR) positive (p = 0.013) than in SH1, but less likely to be ER positive (p < 0.001) or PR positive (p = 0.012) than SH2. Among 15 tumors from TH patients, there was no clear pattern of loss of heterozygosity (LOH) for BRCA1 or BRCA2 in either BC or OC.

CONCLUSIONS

Our observations suggest that clinical TH phenotypes resemble SH1. However, TH breast tumor marker characteristics are phenotypically intermediate to SH1 and SH2.

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.

Low-level constitutional mosaicism of a de novoBRCA1 gene mutation

Background:

Pathogenic BRCA1 mutations are usually inherited. Constitutional low-level BRCA1 mosaicism has never been reported.

Methods:

Next-generation sequencing (NGS) of cancer gene panel of germline and tumour DNA in a patient with early onset, triple-negative breast cancer.

Results:

Constitutional de novo mosaicism (5%) for a pathogenic (c.1953dupG; p.Lys652Glufs*21) BRCA1mutation was detected in leukocytes, buccal tissue and normal breast tissue DNA, with ∼50% mutation in tumorous breast tissue.

Conclusion:

This is the first reported case of low-level, multiple tissue, constitutional mosaicism in BRCA1, and highlights the need to consider deep sequencing in affected individuals clinically suspected of having cancer predisposition whose tumours display a BRCA mutation.

Routine TP53 testing for breast cancer under age 30: ready for prime time?

It is well known that early-onset breast cancer may be due to an inherited predisposition. When evaluating women diagnosed with breast cancer under age 30, two important syndromes are typically considered: Hereditary Breast and Ovarian Cancer Syndrome and Li-Fraumeni syndrome. Many women are offered genetic testing for mutations in the BRCA1 and BRCA2 genes; however, few are offered genetic testing for mutations in the TP53 gene. There is a concern that overly restrictive testing of TP53 may fail to recognize families with Li-Fraumeni syndrome. We reviewed the genetic test results and family histories of all women with early-onset breast cancer who had genetic testing of the TP53 gene at the Toronto Hospital for Sick Children. Of the 28 women tested, six (33.3 %) had a mutation in the TP53 gene; a mutation was found in 7.7 % of women who did not meet current criteria for Li-Fraumeni syndrome. By reviewing similar data published between 2000 and 2011, we estimate that 5-8 % of women diagnosed with early-onset breast cancer, and who have a negative family history, may have a mutation in the TP53 gene. Given the potential benefits versus harms of this testing, we discuss the option of simultaneous testing of all three genes (BRCA1, BRCA2, and TP53) for women diagnosed with breast cancer before age 30.

Double heterozygosity for mutations in BRCA1 and BRCA2 in German breast cancer patients: implications on test strategies and clinical management

Double heterozygosity for disease-causing BRCA1 and BRCA2 mutations is a very rare condition in most populations. Here we describe genetic and clinical data of eight female double heterozygotes (DH) for BRCA1 and BRCA2 mutations found in a cohort of 8162 German breast/ovarian cancer families and compare it with the data of their single heterozygous relatives and of the index patients of the German Consortium for Hereditary Breast and Ovarian Cancer. Furthermore, we analyze the phenotypic features of these patients with respect to age at onset of first cancer, first breast/ovarian cancer and the number of disease manifestations and compare them to that of published Caucasian female DHs and their single heterozygous female relatives. German DHs were not significantly younger at diagnosis of first breast cancer than the single heterozygous index patients of the German Consortium. However, if the data of our study were pooled with that of the literature, DHs were substantially younger at onset of first cancer (mean age 40.4 years, 95 % CI = 36.6-44.1) than their single heterozygous female relatives (mean age 51.9 years, 95 % CI = 46.8-57.0). The two groups also differed concerning the onset of first breast cancer (mean age 40.6 years, 95 % CI = 36.6-44.5 vs. 52.6, 95 % CI = 47.5-57.6). In addition, DHs had a more severe disease than their female relatives carrying a single BRCA mutation (1.4 vs. 0.6 manifestations per person). In contrast to Ashkenazi Jewish females, Caucasian DH females might develop breast cancer at an earlier age and have a more severe disease than single heterozygous BRCA mutation carriers. Therefore, DHs may benefit from more intensive surveillance programs/follow-up care and prophylactic surgery.

A de novo complete BRCA1 gene deletion identified in a Spanish woman with early bilateral breast cancer

BACKGROUND

Germline mutations in either of the two tumor-suppressor genes, BRCA1 and BRCA2, account for a significant proportion of hereditary breast and ovarian cancer cases. Most of these mutations consist of deletions, insertions, nonsense mutations, and splice variants, however an increasing number of large genomic rearrangements have been identified in these genes.

METHODS

We analysed BRCA1 and BRCA2 genes by direct sequencing and MLPA. We confirmed the results by an alternative MLPA kit and characterized the BRCA1 deletion by Array CGH.

RESULTS

We describe the first case of a patient with no strong family history of the disease who developed early-onset bilateral breast cancer with a de novo complete BRCA1 gene deletion in the germinal line. The detected deletion started from the region surrounding the VAT1 locus to the beginning of NBR1 gene, including the RND2, ΨBRCA1, BRCA1 and NBR2 complete genes.

CONCLUSION

This finding supports the large genomic rearrangement screening of BRCA genes in young breast cancer patients without family history, as well as in hereditary breast and ovarian cancer families previously tested negative for other variations.

A novel de novo BRCA1 mutation in a Chinese woman with early onset breast cancer

Germline mutations in the two breast cancer susceptibility genes, BRCA1 and BRCA2 account for a significant portion of hereditary breast/ovarian cancer. De novo mutations such as multiple exon deletion are rarely occurred in BRCA1 and BRCA2. During our mutation screening for BRCA1/2 genes to Chinese women with risk factors for hereditary breast/ovarian cancer, we identified a novel germline mutation, consisting of a deletion from exons 1 to 12 in BRCA1 gene, in a patient diagnosed with early onset triple negative breast cancer with no family history of cancer. None of her parents carried the mutation and molecular analysis showed that this novel de novo germline mutation resulted in down-regulation of BRCA1 gene expression.

Prevalence of BRCA1/2 mutations in sporadic breast/ovarian cancer patients and identification of a novel de novo BRCA1 mutation in a patient diagnosed with late onset breast and ovarian cancer: implications for genetic testing

In order to adequately evaluate the clinical relevance of genetic testing in sporadic breast and ovarian cancer patients, we offered comprehensive BRCA1/2 mutation analysis in patients without a family history for the disease. We evaluated the complete coding and splice site regions of BRCA1/2 in 193 sporadic patients. In addition, a de novo mutation was further investigated with ultra deep sequencing and microsatellite marker analysis. In 17 patients (8.8%), a deleterious germline BRCA1/2 mutation was identified. The highest mutation detection ratio (3/7 = 42.9%) was obtained in sporadic patients diagnosed with breast and ovarian cancer after the age of 40. In 21 bilateral breast cancer patients, two mutations were identified (9.5%). Furthermore, 140 sporadic patients with unilateral breast cancer were investigated. Mutations were only identified in patients diagnosed with breast cancer before the age of 40 (12/128 = 9.4% vs. 0/12 with Dx > 40). No mutations were detected in 17 sporadic male breast cancer and 6 ovarian cancer patients. BRCA1 c.3494_3495delTT was identified in a patient diagnosed with breast and ovarian cancer at the age of 52 and 53, respectively, and was proven to have occurred de novo at the paternal allele. Our study shows that the mutation detection probability in specific patient subsets can be significant, therefore mutation analysis should be considered in sporadic patients. As a consequence, a family history for the disease and an early age of onset should not be used as the only criteria for mutation analysis of BRCA1/2. The relatively high mutation detection ratio suggests that the prevalence of BRCA1/2 may be underestimated, especially in sporadic patients who developed breast and ovarian cancer. In addition, although rare, the possibility of a de novo occurrence in a sporadic patient should be considered.

Hereditary breast and ovarian cancer due to mutations in BRCA1 and BRCA2

Hereditary breast and ovarian cancer due to mutations in the BRCA1 and BRCA2 genes is the most common cause of hereditary forms of both breast and ovarian cancer. The overall prevalence of BRCA1/2 mutations is estimated to be from 1 in 400 to 1 in 800 with a higher prevalence in the Ashkenazi Jewish population (1 in 40). Estimates of penetrance (cancer risk) vary considerably depending on the context in which they were derived and have been shown to vary within families with the same BRCA1/2 mutation. This suggests there is no exact risk estimate that can be applied to all individuals with a BRCA1/2 mutation. The likelihood of harboring a BRCA1 or BRCA2 mutation is dependent on one's personal and/or family history of cancer and can be estimated using various mutation probability models. For those individuals who have a BRCA1 or BRCA2 mutation, several screening and primary prevention options have been suggested, including prophylactic surgery and chemoprevention. Once a BRCA1 or BRCA2 mutation has been identified in a family, testing of at-risk relatives can identify those family members who also have the familial mutation and thus need increased surveillance and early intervention when a cancer is diagnosed.

Case report: de novo BRCA2 gene mutation in a 35-year-old woman with breast cancer

In this report, we describe a patient with a de novo BRCA2 gene mutation (5301insA) who developed early onset breast cancer with no strong family history of the disease. Only three similar instances have been reported previously. Subsequent site-specific analysis in her parents showed that neither carried the mutation previously identified in their daughter. Various possible explanations for this finding were excluded. Paternity was confirmed using 13 highly polymorphic markers, thereby illustrating that the patient carried a de novo mutation in the BRCA2 gene. The 5301insA mutation has been well described and reported many times in the Breast Cancer Information Core online Breast Cancer Mutation database. This finding illustrates the importance of determining the incidence of de novo BRCA mutations and is of significant clinical value to breast cancer prevention and management. Our case report presents the fourth case in which a de novo germline mutation in a BRCA1/2 gene has been identified.

Identification of a de novo BRCA1 mutation in a woman with early onset bilateral breast cancer

De novo mutations are rarely reported in BRCA1 and BRCA2. We report a proven BRCA1 de novo mutation in a woman diagnosed with young onset bilateral breast cancer with a limited family history.

Novel de novo BRCA2 mutation in a patient with a family history of breast cancer

Background

BRCA2 germ-line mutations predispose to breast and ovarian cancer. Mutations are widespread and unclassified splice variants are frequently encountered. We describe the parental origin and functional characterization of a novel de novo BRCA2 splice site mutation found in a patient exhibiting a ductal carcinoma at the age of 40.

Methods

Variations were identified by denaturing high performance liquid chromatography (dHPLC) and sequencing of the BRCA1 and BRCA2 genes. The effect of the mutation on splicing was examined by exon trapping in COS-7 cells and by RT-PCR on RNA isolated from whole blood. The paternity was determined by single nucleotide polymorphism (SNP) microarray analysis. Parental origin of the de novo mutation was determined by establishing mutation-SNP haplotypes by variant specific PCR, while de novo and mosaic status was investigated by sequencing of DNA from leucocytes and carcinoma tissue.

Results

A novel BRCA2 variant in the splice donor site of exon 21 (nucleotide 8982+1 G→A/c.8754+1 G→A) was identified. Exon trapping showed that the mutation activates a cryptic splice site 46 base pairs 3' of exon 21, resulting in the inclusion of a premature stop codon and synthesis of a truncated BRCA2 protein. The aberrant splicing was verified by RT-PCR analysis on RNA isolated from whole blood of the affected patient. The mutation was not found in any of the patient's parents or in the mother's carcinoma, showing it is a de novo mutation. Variant specific PCR indicates that the mutation arose in the male germ-line.

Conclusion

We conclude that the novel BRCA2 splice variant is a de novo mutation introduced in the male spermatozoa that can be classified as a disease causing mutation.

Validation study of the LAMBDA model for predicting the BRCA1 or BRCA2 mutation carrier status of North American Ashkenazi Jewish women

LAMBDA is a model that estimates the probability an Ashkenazi Jewish (AJ) woman carries an ancestral BRCA1 or BRCA2 mutation from her personal and family cancer history. LAMBDA is relevant to clinical practice, and its implementation does not require a computer. It was developed principally from Australian and UK data. We conducted a validation study using 1286 North American AJ women tested for the mutations 185delAG and 5382insC in BRCA1 and 6174delT in BRCA2. Most had a personal or family history of breast cancer. We observed 197 carriers. The area under the receiver operator characteristic (ROC) curve (a measure of ranking) was 0.79 [95% confidence interval (CI) = 0.77-0.81], similar to that for the model-generating data (0.78; 95% CI = 0.75-0.82). LAMBDA predicted 232 carriers (18% more than observed; p = 0.002) and was overdispersed (p = 0.009). The Bayesian computer program BRCAPRO gave a similar area under the ROC curve (0.78; 95% CI = 0.76-0.80), but predicted 367 carriers (86% more than observed; p < 0.0001), and was substantially overdispersed (p < 0.0001). Therefore, LAMBDA is comparable to BRCAPRO for ranking AJ women according to their probability of being a BRCA1 or BRCA2 mutation carrier and is more accurate than brcapro which substantially overpredicts carriers in this population.

BRCA1, BRCA2, TP53, and CDKN2A germline mutations in patients with breast cancer and cutaneous melanoma

PURPOSE

From epidemiological studies it appears that breast cancer (BC) and cutaneous melanoma (CMM) in the same individual occur at a higher frequency than expected by chance. Genetic factors common to both cancers can be suspected. Our goal was to estimate the involvement of "high risk" genes in patients presenting these two neoplasia, selected irrespectively from family history and age at diagnosis.

EXPERIMENTAL DESIGN

Eighty two patients with BC and CMM were screened for BRCA1, BRCA2, TP53, CDKN2A and CDK4 (exon 2) germline mutations.

RESULTS

Deleterious mutations were identified in 6 patients: two carriers of a BRCA1 germline mutation, two carriers of TP53 germline mutations (one of which also harbored a BRCA2 deleterious mutation, the other one a BRCA2 unclassified variant), and two carriers of a CDKN2A germline mutation. In addition, 6 variants of unknown signification were identified in BRCA1 or BRCA2 genes. Regarding family history, 3/13 (23%) patients with a positive family history of BC or CMM were carriers of a germline mutation, whereas only 3/69 (4%) patients without family history were carriers of a germline mutation.

CONCLUSION

Our findings show that few patients with BC and CMM who lacked family histories of these cancers are carriers of deleterious germline mutations in four of the five genes we examined. We describe for the first time, two simultaneous BRCA2 and TP53 mutations, suggesting that analysis in more than one gene could be performed if a patient's personal or familial history does not match a single syndrome.

Concomitant BRCA1 and BRCA2 gene mutations in an Ashkenazi Jewish woman with primary breast and ovarian cancer

We describe an unusual Ashkenazi Jewish patient with breast and epithelial ovarian cancer who was found to have simultaneous BRCA1 and BRCA2 mutations (BRCA1 5382insC and BRCA2 6174delT). While these mutations are known to occur individually in Ashkenazi Jewish women, concomitant BRCA1 and BRCA2 mutations in the same individual are rare.

Phenotype-directed analysis of genotype in early-onset, familial breast cancers

Considerable heterogeneity of morphology and disease outcome exists within breast cancers (BC), which likely reflects variable molecular pathogeneses within this broad clinical group.

AIM

To evaluate the underlying genomic alterations associated with familial, early-onset BC (EOBC) phenotypes, in order to improve the management of this disease.

METHODS

Using hierarchical clustering of morphological and immunophenotypical parameters, 116 EOBC were stratified into six groups. Conventional and array-based comparative genomic hybridisation was used to analyse the genomic alterations.

RESULTS

Specific areas of genomic imbalance were associated with individual phenotypes. The largest phenotypical group was high grade, oestrogen receptor and HER-2 negative. This group contained the majority of BRCA1 germline mutation-associated tumours and commonly showed loss of chromosomal regions 5cent-5q13, 5q14-22 and 4q28-32. High mitotic rate, an important indicator of tumour cell proliferation and poor prognosis, was associated with gain of 19p, mapped within 7 Mb of the telomere. This region contains the candidate oncogene CDC34, the protein product of which is involved in ubiquitin-mediated degradation of the cyclin-dependent kinase inhibitor, p27Kip1.

CONCLUSION

Phenotype-based analysis can be used to determine the genetic changes important in subtypes of BC. Further, the different morphological phenotypes could act as a cost-effective surrogate for genotypical stratification to facilitate optimal management of this disease.

Double heterozygotes for non-Caucasian families with mutations in BRCA-1 and BRCA-2 genes

The recent discovery of the BRCA-1 and BRCA-2 genes as contributing factors to hereditary breast cancer has significantly improved our understanding of familial breast cancer. Deleterious mutations in both BRCA-1 and BRCA-2 in an individual patient is exceedingly rare, with few case reports in the literature, particularly among non-Caucasian, non-Jewish families. We describe here two cases of deleterious mutations in both genes in a cohort of Korean women with early onset breast cancer.

Genetic and histopathologic evaluation of BRCA1 and BRCA2 DNA sequence variants of unknown clinical significance

Classification of rare missense variants as neutral or disease causing is a challenge and has important implications for genetic counseling. A multifactorial likelihood model for classification of unclassified variants in BRCA1 and BRCA2 has previously been developed, which uses data on co-occurrence of the unclassified variant with pathogenic mutations in the same gene, cosegregation of the unclassified variant with affected status, and Grantham analysis of the fit between the missense substitution and the evolutionary range of variation observed at its position in the protein. We have further developed this model to take into account relevant features of BRCA1- and BRCA2-associated tumors, such as the characteristic histopathology and immunochemical profiles associated with pathogenic mutations in BRCA1, and the fact that approximately 80% of tumors from BRCA1 and BRCA2 carriers undergo inactivation of the wild-type allele by loss of heterozygosity. We examined 10 BRCA1 and 15 BRCA2 unclassified variants identified in Australian, multiple-case breast cancer families. By a combination of genetic, in silico, and histopathologic analyses, we were able to classify one BRCA1 variant as pathogenic and six BRCA1 and seven BRCA2 variants as neutral. Five of these neutral variants were also found in at least 1 of 180 healthy controls, suggesting that screening a large number of appropriate controls might be a useful adjunct to other methods for evaluation of unclassified variants.

Retinoblastoma and hypochondroplasia: a case report of two germline mutations arising simultaneously

PURPOSE

To report a rare case of a patient with two germline mutations arising de novo resulting in bilateral retinoblastoma and hypochondroplasia.

DESIGN

A brief review about retinoblastoma and hypochondroplasia; a case report with genetic mutational analysis results.

CASE REPORT

We report a patient manifesting the clinical features of both bilateral retinoblastoma and hypochondroplasia. Genetic analysis revealed two germline mutations, a seven base-pair deletion in exon 12 (G70313-703129del) in one allele of the retinoblastoma gene (RB1) and the N540K (C1620C > A) mutation in one allele of the fibroblast growth factor 3 (FGFR3) gene, a frequent mutation in hypochondroplasia. Neither parent has a personal or family history of cancer or ocular tumors. Only the patient's mother is short in stature, and her genetic analysis revealed no FGFR3 mutations.

CONCLUSIONS

Although the probability of both germline mutations occurring in a single individual is exceedingly low, the etiology and mechanism are unknown in this patient. To the best of our knowledge, this is the first report of two clinically distinct heritable germline mutations arising de novo in an individual.

The androgen receptor CAG repeat polymorphism and modification of breast cancer risk in BRCA1 and BRCA2 mutation carriers

Introduction

The androgen receptor (AR) gene exon 1 CAG repeat polymorphism encodes a string of 9–32 glutamines. Women with germline BRCA1 mutations who carry at least one AR allele with 28 or more repeats have been reported to have an earlier age at onset of breast cancer.

Methods

A total of 604 living female Australian and British BRCA1 and/or BRCA2 mutation carriers from 376 families were genotyped for the AR CAG repeat polymorphism. The association between AR genotype and disease risk was assessed using Cox regression. AR genotype was analyzed as a dichotomous covariate using cut-points previously reported to be associated with increased risk among BRCA1 mutation carriers, and as a continuous variable considering smaller allele, larger allele and average allele size.

Results

There was no evidence that the AR CAG repeat polymorphism modified disease risk in the 376 BRCA1 or 219 BRCA2 mutation carriers screened successfully. The rate ratio associated with possession of at least one allele with 28 or more CAG repeats was 0.74 (95% confidence interval 0.42–1.29; P = 0.3) for BRCA1 carriers, and 1.12 (95% confidence interval 0.55–2.25; P = 0.8) for BRCA2 carriers.

Conclusion

The AR exon 1 CAG repeat polymorphism does not appear to have an effect on breast cancer risk in BRCA1 or BRCA2 mutation carriers.

Italian family with two independent mutations: 3358T/A in BRCA1 and 8756delA in BRCA2 genes

Hereditary breast/ovarian cancer is a well-characterized clinical entity, largely attributed to the inheritance of BRCA1 or BRCA2 mutations. Among general population, the mutation's frequency of these genes is very low; therefore, the identification of two independent mutations in the same family is a rare event. This study reports the presence of two mutations, one in the BRCA1 and the second in the BRCA2 gene in an Italian Caucasian kindred. This family is composed of more than 250 individuals, spanning through five generations, among which endogamy was a common phenomenon. Considering the tumor spectrum, this family is characterized by a high incidence of different types of cancer. In our study, we considered only three out of seven family units for BRCA1 and BRCA2 analysis. In one of the family units, we found independent mutations of both BRCA genes. The BRCA1 mutation on exon 11 (3358T-->A) was identified originally in the index case and subsequently in 18 members of this family, whereas the same mutation was not detected in a related family member with male breast cancer. The male breast cancer patient led to the identification, through mutational analysis, of a new BRCA2 mutation (8756delA). This BRCA2 mutation was also found in the male breast cancer patient's daughter. The discovery of the BRCA2 mutation allowed us to alert the patient's daughter who, otherwise, could be falsely reassured since she had a negative BRCA1 test.

Risk assessment & genetic testing

Ovarian cancer is the fifth most common cause of cancer death in women in Western countries and family history is one of the strongest known risk factors. Approximately 5 to 13% of all ovarian cancer cases are caused by the inheritance of cancer predisposing genes with an autosomal pattern of transmission. The inherited fraction of ovarian cancer may differ between populations. Based on analysis of familial ovarian cancer pedigrees and other epidemiological studies, three hereditary ovarian cancer syndromes have been defined. The identification of the genes responsible for most hereditary ovarian cancers has open a new area of early detection methods and preventive procedures specifically dedicated to women identified as carrying ovarian cancer predisposing genes. Predictive oncology is best performed by a dedicated unit with professionals aware of all the issues surrounding genetic testing.

Germline mutations in BRCA1 and BRCA2 in breast-ovarian families from a breast cancer risk evaluation clinic

PURPOSE

Data from the Breast Cancer Linkage Consortium suggest that the proportion of familial breast and ovarian cancers linked to BRCA1 or BRCA2 may be as high as 98% depending on the characteristics of the families, suggesting that mutations in BRCA1 or BRCA2 may entirely account for hereditary breast and ovarian cancer families. We sought to determine what proportion of families with both breast and ovarian cancers seen in a breast cancer risk evaluation clinic are accounted for by coding region germline mutations in BRCA1 and BRCA2 as compared to a linkage study group. We also evaluated what clinical parameters were predictive of mutation status.

PATIENTS AND METHODS

Affected women from 100 families with at least one case of breast cancer and at least one case of ovarian cancer in the same lineage were screened for germline mutations in the entire coding regions of BRCA1 and BRCA2 by conformation-sensitive gel electrophoresis, a polymerase chain reaction-based heteroduplex analysis, or direct sequencing.

RESULTS

Unequivocal deleterious mutations were found in 55% (55 of 100) of the families studied. Mutations in BRCA1 and BRCA2 accounted for 80% and 20% of the mutations overall, respectively. Using multivariate analysis, the strongest predictors of detecting a mutation in BRCA1 or BRCA2 in this study group were the presence of a single family member with both breast and ovarian cancer (P <.0009; odds ratio [OR], 5.68; 95% confidence interval [CI], 2.04 to 15.76) and a young average age at breast cancer diagnosis in the family (P <.0016; OR, 1.69; 95% CI, 1.23 to 2.38).

CONCLUSION

These results suggest that at least half of breast/ovarian families evaluated in a high-risk cancer evaluation clinic may have germline mutations in BRCA1 or BRCA2. Whether the remaining families have mutations in noncoding regions in BRCA1, mutations in other, as-yet-unidentified, low-penetrance susceptibility genes, or represent chance clustering remains to be determined.

After BRCA1 and BRCA2-what next? Multifactorial segregation analyses of three-generation, population-based Australian families affected by female breast cancer

Mutations in BRCA1 and BRCA2 that cause a dominantly inherited high risk of female breast cancer seem to explain only a small proportion of the aggregation of the disease. To study the possible additional genetic components, we conducted single-locus and two-locus segregation analyses, with and without a polygenic background, using three-generation families ascertained through 858 women with breast cancer diagnosed at age <40 years, ascertained through population cancer registries in Melbourne and Sydney, Australia. Extensive testing for deleterious mutations in BRCA1 and BRCA2, to date, has identified 34 carriers. Our analysis suggested that, after other possible unmeasured familial factors are adjusted for and the known BRCA1 and BRCA2 mutation carriers are excluded, there appears to be a residual dominantly inherited risk of female breast cancer in addition to that derived from mutations in BRCA1 and BRCA2. This study also suggests that there is a substantial recessively inherited risk of early-onset breast cancer. According to the best-fitting model, after excluding known carriers of mutations in BRCA1 and BRCA2, about 1/250 (95% confidence interval [CI] 1/500 to 1/125) women have a recessive risk of 86% (95% CI 69%-100%) by age 50 years and of almost 100% by age 60 years. Possible reasons that our study has implicated a novel strong recessive effect include our inclusion of data on lineal aunts and grandmothers, study of families ascertained through women with early-onset breast cancer, allowance for multiple familial factors in the analysis, and removal of families for whom the cause (i.e., BRCA1 or BRCA2) is known. Our findings may have implications for attempts to identify new breast cancer-susceptibility genes.

De novo recurrent germline mutation of the BRCA2 gene in a patient with early onset breast cancer

Germline mutations in either of the two major breast cancer predisposition genes, BRCA1 and BRCA2, account for a significant proportion of hereditary breast/ovarian cancer. Identification of breast cancer patients carrying mutations of these genes is primarily based on a positive family history of breast/ovarian cancer or early onset of the disease or both. In the course of mutation screening of the BRCA1 and BRCA2 genes in a hospital based series of patients with risk factors for hereditary breast/ovarian cancer, we identified a germline mutation in the BRCA2 gene (3034del4) in a patient with early onset breast cancer and no strong family history of the disease. Subsequent molecular analysis in her parents showed that neither of them carried the mutation. Paternity was confirmed using a set of highly polymorphic markers, showing that the proband carried a de novo germline mutation in the BRCA2 gene. Interestingly, 3034del4 is a recurrent mutation occurring in a putative mutation prone region of the BRCA2 gene. Our study presents the first case in which a de novo germline mutation in the BRCA2 gene has been identified, and supports previous results of haplotype studies, confirming that the 3034del4 mutation has multiple independent origins.

Hereditary cancer syndromes

OBJECTIVE

To summarize the biological basis, clinical implications, identification, and medical management of syndromes associated with increased risk of common adult cancers.

DATA SOURCES

Recent studies and data available from molecular and clinical analysis of genes responsible for autosomal-dominant inheritance of cancer risk.

DATA SYNTHESIS

Several hereditary cancer syndromes have been identified for which there are increasingly effective diagnostic and management options. Specific hereditary susceptibility syndromes have been characterized that increase the risk of malignancies of the breast, ovary, colon, endometrium, and endocrine organs. Following a summary of the biological basis of hereditary cancer risk in adults, the identification of such syndromes by clinical and laboratory means is reviewed. Finally, management options for individuals with these syndromes are summarized.

CONCLUSIONS

Advances in gene discovery have allowed the diagnosis of recently characterized hereditary cancer syndromes to enhance medical management for individuals with inherited susceptibility to common cancers.