Effects of chemotherapy on contralateral breast cancer risk in BRCA1 and BRCA2 mutation carriers: A nationwide cohort study

AimBRCA1/2 mutation carriers with primary breast cancer (PBC) are at high risk of contralateral breast cancer (CBC). In a nationwide cohort, we investigated the effects of chemotherapeutic agents given for PBC on CBC risk separately in BRCA1 and BRCA2 mutation carriers.Patients and methodsBRCA1 or BRCA2 mutation carriers with an invasive PBC diagnosis from 1990 to 2017 were selected from a Dutch cohort. We estimated cumulative CBC incidence using competing risks analysis. Hazard ratios (HR) for the effect of neo-adjuvant or adjuvant chemotherapy and different chemotherapeutic agents on CBC risk were estimated using Cox regression.ResultsWe included 1090 BRCA1 and 568 BRCA2 mutation carriers; median follow-up was 8.9 and 8.4 years, respectively. Ten-year cumulative CBC incidence for treatment with and without chemotherapy was 6.7% [95%CI: 5.1–8.6] and 16.7% [95%CI: 10.8–23.7] in BRCA1 and 4.8% [95%CI: 2.7–7.8] and 16.0% [95%CI: 9.3–24.4] in BRCA2 mutation carriers, respectively. Chemotherapy was associated with reduced CBC risk in BRCA1 (multivariable HR: 0.46, 95%CI: 0.29–0.74); a similar trend was observed in BRCA2 mutation carriers (HR: 0.63, 95%CI: 0.29–1.39). In BRCA1, risk reduction was most pronounced in the first 5 years (HR: 0.32, 95%CI: 0.17–0.61). Anthracyclines and the combination of anthracyclines with taxanes were associated with substantial CBC risk reduction in BRCA1 carriers (HR: 0.34, 95%CI: 0.17–0.68 and HR: 0.22, 95%CI: 0.08–0.62, respectively).ConclusionRisk-reducing effects of chemotherapy are substantial for at least 5 years and may be used in personalised CBC risk prediction in any case for BRCA1 mutation carriers.     

NOEY2 mutations in primary breast cancers and breast hyperplasia

PurposeThe NOEY2 gene mutations and protein expression in human breast cancers, adjacent breast tissues and breast benign lesions were analysed to explore the potential correlation between the mutation spectrum and breast cancer development and progression.Experimental designThe promoter, exon and intron regions of NOEY2 gene were amplified by polymerase chain reaction (PCR) with DNA extracted from 50 human breast cancer and corresponding adjacent breast tissues as well as 50 breast benign lesions, respectively. The PCR products were then sequenced and analysed. The effect of mutations on the expression of NOEY2 protein by immunohistochemistry were proven as well.ResultsTwenty-one of 50 (42%) breast cancer mutations were identified in promoter (11 cases) and exon 2 (seven cases on untranslation region and three on coding region) and 17 of 50 (34%) adjacent breast tissues (all were atypical hyperplasia lesions) occurred mutations, including six promoter mutations and 11 exon 2 changes (10 cases on untranslation region and one on coding region). Interestingly, the mutations were identified in both breast cancers and the corresponding adjacent breast tissues collected from the same patient in seven of them. No mutation was identified in all benign breast tissues. Immunohistochemical analysis showed that two of 17 mutational adjacent breast tissue samples were NOEY2 immunoreaction negative, and in all 21 mutations of breast cancers five cases were of loss of NOEY2 expression. All mutations with immunoreaction negative factor were located at promoter and/or exon 2 coding region. NOEY2 gene mutations were not correlated with patient ages, histological types, tumour sizes, histological grades, clinical stages, axillary lymph node metastases or with the condition of hormone receptor (ER, PR) expression and HER2 amplification.ConclusionsThe mutations of human NOEY2 were identified in human breast cancers and the corresponding adjacent breast tissues. The hot mutation spots were its promoter and exon 2 regions, and those occurring at the exon2 coding region and part of the promoter may alter the expression of NOEY2. The presence of NOEY2 mutations in human breast cancer and early-stage lesions indicates that NOEY2 mutations may be partly associated with breast tumourigenesis.     

XRCC1 gene polymorphisms and breast cancer risk in different populations: A meta-analysis

We performed a meta-analysis to investigate the role of XRCC1 polymorphisms Arg194Trp, Arg280His and Arg399Gln in breast cancer. The results were pooled in a manner that appropriately reflects a biological model of gene effect using a random effects logistic regression model without multiple comparisons. Forty studies from 31 reports were included with 10 465 cases and 10 888 controls at Arg194Trp, 6156 cases and 5806 controls at Arg280His, and 21 467 cases and 22 766 controls at Arg399Gln. Our analysis found a tendency towards a recessive effect of Arg280His variant in Asian population only (His/His vs. Arg/Arg + Arg/His: OR = 2.27, 95% CI = 0.82, 6.31). An increased breast cancer risk with a recessive effect was also suggested for Arg399Gln variant in Asian population (Gln/Gln vs. Arg/Arg + Arg/Gln: OR = 1.59, 95% CI = 1.22, 2.09) only. These findings suggest that polymorphisms Arg280His and Arg399Gln may modify breast cancer risk differently in Caucasian and Asian populations.     

Management of breast cancer risk in BRCA1/2 mutation carriers who are unaffected with cancer

Pathogenic mutations in BRCA1 and BRCA2 genes markedly increase the risk of breast cancer and other cancers such as ovarian/fallopian tube, pancreatic, prostate, and melanoma. Patients with BRCA1 mutations have a slightly higher lifetime risk of breast cancer than BRCA2 mutation carriers, and both BRCA1 and BRCA2 carriers tend to develop breast cancer at an earlier age than the general population. In this review, we will discuss management recommendations to reduce breast cancer risk for BRCA1/2 mutation carriers including special populations of carriers such as pregnant or lactating patients and men. Breast cancer screening, including clinical breast examination, mammogram, and breast MRI, is important for detecting breast cancer at an early and likely curable stage. In addition to screening, counseling on risk‐reducing surgeries is strongly recommended for BRCA1/2 carriers. Risk‐reducing mastectomy decreases the risk of breast cancer development, and risk‐reducing salpingo‐oophorectomy decreases ovarian cancer‐specific as well as overall mortality, but controversy exists regarding its impact on breast cancer‐specific mortality. Given the effectiveness of screening for breast cancer, further management should be carried out on an individual basis taking into account quality of life and psychosocial factors, and recommendations should be readdressed periodically as science progresses and patients’ goals may change.     

Post-mastectomy surveillance of BRCA1/BRCA2 mutation carriers: Outcomes from a specialized clinic for high-risk breast cancer patients

Female BRCA1/BRCA2 mutation carriers may elect bilateral risk-reducing mastectomy. There is a paucity of data on yield of imaging surveillance after risk-reducing mastectomy. This retrospective study focused on female BRCA1/BRCA2 mutation carriers who underwent bilateral mastectomy either as primary preventative, or as secondary preventative, after breast cancer diagnosis. All participants underwent breast imaging at 6- to 12-month intervals after mastectomy. Data on subsequent breast cancer diagnosis and timing were collected and compared between the groups. Overall, 184 female mutation carriers (134 BRCA1, 45 BRCA2, 5 both BRCA genes) underwent bilateral mastectomy after initial breast cancer diagnosis, between April 1, 2009 and August 31, 2018. During a mean follow-up of 6.2 ± 4.2 years, 13 (7.06%) were diagnosed with breast cancer; 12 ipsilateral (range: 0.4–28.8 years) and 1 contralateral breast cancer, 15.9 years after surgery. On the contrary, among asymptomatic BRCA1 (n = 40) and BRCA2 (n = 13) mutation carriers who underwent primary risk-reducing mastectomy (mean age at surgery 39.5 ± 8.4 years); none has developed breast cancer after a mean follow-up of 5.4 ± 3.4 years. BRCA1/BRCA2 mutation carriers with prior disease who underwent risk-reducing mastectomy after breast cancer diagnosis are still prone for developing ipsi or contralateral breast cancer, and therefore may benefit from continues clinical and imaging surveillance, unlike BRCA1/BRCA2 mutation carriers who undergo primary preventative bilateral mastectomy.     

The prevalence of germline BRCA1 and BRCA2 mutations in young women with breast cancer undergoing breast-conservation therapy

BACKGROUND: Germline mutations of BRCA1 and BRCA2 increase the risk for breast cancer. Mutation carriers selecting breast-conservation therapy (BCT) for treatment of operable breast cancer experience a higher rate of new primary breast cancers. We sought to determine the frequency of BRCA1/BRCA2 mutations in women who underwent BCT. Genetic testing results were compared with the prior probability of mutations in either gene. METHODS: Eighty-nine patients age 39 or younger entered the study. Genetic testing was performed for BRCA1 and BRCA2 and the BRCAPRO model determined the probability of carrying a mutation. RESULTS: Eight mutations were discovered (prevalence, 9.0%). Twenty (22%) uncharacterized sequence variants were found. The prior probability of carrying a mutation was 14%. Mutation carriers had a higher prior probability (.49) compared with women with uncharacterized variants (.09) or with normal genes (.11). CONCLUSIONS: BRCA1 and BRCA2 mutations are common (9%) among unselected young breast cancer patients undergoing BCT.     

Germline mutation screening of the Saethre-Chotzen-associated genes TWIST1 and FGFR3 in families with BRCA1/2-negative breast cancer

Saethre-Chotzen syndrome is one of the most common craniosynostosis syndromes. It is an autosomal dominantly inherited disorder with variable expression that is caused by germline mutations in the TWIST1 gene or more rarely in the FGFR2 or FGFR3 genes. We have previously reported that patients with Saethre-Chotzen syndrome have an increased risk of developing breast cancer. Here we have analysed a cohort of 26 women with BRCA1/2-negative hereditary breast cancer to study whether a proportion of these families might have mutations in Saethre-Chotzen-associated genes. DNA sequence analysis of TWIST1 showed no pathogenic mutations in the coding sequence in any of the 26 patients. MLPA (multiplex ligation-dependent probe amplification)-analysis also showed no alterations in copy numbers in any of the craniofacial disorder genes MSX2, ALX4, RUNX2, EFNB1, TWIST1, FGFR1, FGFR2,FGFR3, or FGFR4. Taken together, our findings indicate that mutations in Saethre-Chotzen-associated genes are uncommon or absent in BRCA1/2-negative patients with hereditary breast cancer.     

BRCA1/2基因突变对乳腺癌保乳术后局部复发的影响及相关预后模型的构建

背景与目的 保乳手术现已成为乳腺癌的标准手术方式之一,保乳手术能够保留患者的乳房外形,极大地改善患者术后的心理状态和生活质量。BRCA1/2基因是与乳腺癌密切相关的易感基因,BRCA1/2基因突变对保乳术后乳腺癌患者局部复发的影响目前尚有争议。因此,本研究分析BRCA1/2基因突变与乳腺癌保乳术后局部复发的关系,并构建相关预测模型,预测保乳术后乳腺癌患者的无局部复发生存（LRFS）率,为乳腺癌患者保乳手术适应证的选择提供可靠的依据。方法 回顾性分析2014年6月—2016年6月于中国人民解放军空军军医大学第一附属医院进行保乳手术的189例乳腺癌患者临床资料,并比较不同临床病理特征下患者BRCA1/2基因突变的差异,通过单因素及多因素Cox等比例回归模型分析BRCA1/2基因突变及其它临床病理因素对乳腺癌患者保乳术后局部复发的影响,并构建列线图来预测患者的LRFS率。通过一致性指数（C-index）、受试者工作特征（ROC）曲线及曲线下面积（AUC）对模型进行内部验证,通过校准曲线评估模型的准确性,并通过临床决策曲线分析（DCA）评价模型的临床获益和应用价值。结果 BRCA1/2基因突变组和未突变组的年龄和分子分型进行差异有统计学意义（均P<0.05）。单因素Cox等比例回归模型分析结果显示,BRCA1/2突变、肿瘤分级、肿瘤大小、N分期及分子分型是保乳术后乳腺癌患者LRFS率的影响因素（均P<0.1）。多因素Cox等比例回归模型分析结果显示,BRCA1/2基因突变、肿瘤大小、N分期及分子分型是保乳术后乳腺癌患者局部复发的独立影响因素（P<0.05）。将这些因素纳入并建立LRFS率的列线图预测模型。模型的C-index为0.86,内部验证C-index为0.81。ROC曲线分析结果显示,模型的3、5年LRFS率预测的AUC分别为0.89、0.85;校准曲线显示列线图预测的LRFS率与实际LRFS率接近;DCA分析显示模型的临床获益及应用价值较高。结论 BRCA1/2基因突变与保乳术后乳腺癌患者的局部复发相关,基于BRCA1/2基因突变列线图模型能够准确地预测保乳术后乳腺癌患者的LRFS率,并为乳腺癌患者手术方式的选择提供有效的科学依据。     

Efficacy of anthracycline/taxane‐based neo‐adjuvant chemotherapy on triple‐negative breast cancer in BRCA1/BRCA2 mutation carriers

This study aims to estimate the pathologic complete response (pCR) rate after neo‐adjuvant chemotherapy and to compare disease‐free survival (DFS) and overall survival (OS) between pCR and non‐pCR groups of patients with triple‐negative breast cancer (TNBC) and deleterious BRCA1 or BRCA2 mutation. We carried out a retrospective analysis of 53 patients including 46 BRCA1, 6 BRCA2, and 1 combined BRCA1 and BRCA2 mutation. All patients had been diagnosed with triple‐negative breast cancer (TNBC) between 1997 and 2014. Neo‐adjuvant therapy consisted of regimens that were based on anthracycline or an anthracycline‐taxane doublet. DFS included any relapse or second cancer. The Kaplan‐Meier method and the log‐rank test were used to compare pCR and non‐pCR groups. A pCR was observed in 23 (42.6% [95% CI, 29.2%‐56.8%]) of the TNBC included. The pCR rate was 38.3% [95% CI, 26%‐55%] among BRCA1 mutation carriers, and 66% among the 6 BRCA2 mutation carriers. Median follow‐up was 4.4 years (range 0.62‐16.2 years) and did not differ between the groups (P = .25). Fifteen relapses and six second cancers were recorded during the follow‐up period. Eleven deaths occurred, all of which were in the non‐pCR group. DFS (P < .01) and OS (P < .01) were significantly better in the pCR group than the non‐pCR group. This study shows a high pCR rate after neo‐adjuvant therapy in BRCA‐mutated triple‐negative breast cancer, and the survival results confirm the prognostic value of pCR in this group. These outcomes should be considered as a basis of comparison to be used by future studies about new therapies in this domain.     

Prophylactic surgery to reduce breast cancer risk: a brief literature review

Prophylactic mastectomy reduces the likehood of developing breast cancer among women at heightened risk for breast cancer, but at significant personal cost.Women at increased breast cancer risk on the basis of hormonal history, family history and/or genetic mutation carrier status may consider bilateral prophylactic mastectomy with or without reconstruction to reduce their cancer risk and/or decrease their chances of cancer mortality. Women having received mastectomy as treatment for breast cancer may request contralateral mastectomy to decrease the chances of developing a second breast primary. The potential oncologic value of these procedures must be weighed carefully on a case -by-case basis against the operation's physical and psychological morbidity. The purppose of this literature review is to provide a practice-oriented summary of recent clinical studies attempting to address the relative risks and benefits of preventive surgery for breast cancer. Data are included regarding the psychological factors surrounding patient selection and quality of life outcomes, which become the cornerstone of patient satisfaction and acceptance. Taken together, these data support the Society of Surgical Oncology position statement regarding the proper application of prophylactic surgery for breast cancer.     

BRCA mutation characteristics in a series of index cases of breast cancer selected independent of family history

Certain genetic predisposition factors, such as BRCA1 and BRCA2 mutations play a pivotal role in familial breast cancer development in both males and females. Due to this, the importance and necessity of genetic screening to identify mutations affecting the population is paramount. Undergoing genetic screenings allows for a more knowledgeable risk assessment for the patients and their care providers. The aim of this study was to evaluate the prevalence of BRCA1/BRCA2 mutated genes in the Turkish population among unselected patients. To identify the molecular markers, we utilized a gene panel analysis consisting of BRCA1 and BRCA2 genes, with a next generation sequencing platform (MiSeq System, Illumina). Sequencing was performed using leukocyte DNA from breast cancer patients. In‐silico analysis for novel mutations was carried out using SIFT, PolyPhen2 and MutationTaster. BRCA1 and BRCA2 pathogenic variants were identified in 18 of 129 (14%) patients among the study population; of those 18 patients, seven (39%) were found in the BRCA1 gene and 11 (61%) in the BRCA2 gene. Ten of the eleven BRCA2 variants (90%) were novel mutations. Four of ten (40%) of the novel mutations were determined to be deleterious and six out of ten (60%) were identified as single nucleotide variations. Clinically significant mutations of the BRCA1/BRCA2 genes are related to an increased susceptibility for breast cancer. There is however, little known about BRCA mutations amongst the general population. Thus, it is important that patients are able to undergo genetic screenings and counseling. This also allows for greater care from health care providers and can only facilitate disease prevention which in turn can lead to a decreased cancer morbidity rate.     

The role of BRCA1 and BRCA2 in prostate cancer

One of the strongest risk factors for prostate cancer is a family history of the disease. Germline mutations in the breast cancer predisposition gene 2 (BRCA2) are the genetic events known to date that confer the highest risk of prostate cancer (8.6-fold in men ≤65 years). Although the role of BRCA2 and BRCA1 in prostate tumorigenesis remains unrevealed, deleterious mutations in both genes have been associated with more aggressive disease and poor clinical outcomes. The increasing incidence of prostate cancer worldwide supports the need for new methods to predict outcome and identify patients with potentially lethal forms of the disease. As we present here, BRCA germline mutations, mainly in the BRCA2 gene, are one of those predictive factors. We will also discuss the implications of these mutations in the management of prostate cancer and hypothesize on the potential for the development of strategies for sporadic cases with similar characteristics.     

Male BRCA1 and BRCA2 mutation carriers: a pilot study investigating medical characteristics of patients participating in a prostate cancer prevention clinic

BACKGROUND: Male BRCA1 and BRCA2 mutation carriers are at an increased risk to develop prostate cancer and are subject to screening protocols for high-risk men. The utility of targeted screening, and the clinical and pathological features associated with prostate cancer, have received little attention in this population. METHODS: We report on the clinical screening and pathological characteristics of a group of 19 men with BRCA1 or BRCA2 mutation, as compared to an age-matched group of men with a family history of prostate cancer. RESULTS: Mutation carriers were significantly more likely to have an elevated PSA at first visit (P = 0.03). Prostate cancer was twice as likely to be diagnosed in mutation carriers although this difference was not statistically significant (P = 0.55). CONCLUSIONS: Prostate cancer surveillance of BRCA1 and BRCA2 mutation carriers is warranted. Further research on larger cohorts is needed to evaluate whether unique pathological prostate cancer characteristics exist in these men.     

BRCA1和BRCA2在胶东半岛地区女性散发性乳腺癌中的表达研究

Objective To study the expression and clinical significance of BRCA1 and BRCA2 in sporadic breast cancer in women of Jiaodong peninsula. Methods Immunohistochemistry and tissue array were used to detect the expression of BRCA1 and BRCA2 in 100 cases of sporadic breast cancer and 30 cases of benign breast tumor in women of Jiaodong peninsula. Results ① The expression rate of BRCA1 and BRCA2 was 49% (49/100) and 50% (50/100) in breast cancer, 80% (24/30) and 83.33% (25/30) in benign breast lesions respectively. The expression rate of BRCA1 and BRCA2 in breast cancer was lower than that in benign breast lesions (P<0.05). ② The expression of BRCA1 and BRCA2 was uncorrelated with factors such as tumor size, lymphatic metastases, age and menopause or not(P>0.05). ③ There was no dependency between the expression of BRCA1 and BRCA2 (P> 0. 05). Conclusions The expression rate of BRCA1 and BRCA2 in breast carcinoma in women of Jiaodong peninsula was lower than that in benign breast lesions, suggesting that the expression of BRCA1 and BRCA2 was related to the occurrence of sporadic breast carcinoma in women of Jiaodong peninsula. However, the role of BRCA1 and BRCA2 in the genesis and development of the breast carcinoma is independent.     

Glutathione S-transferase polymorphisms associated with risk of breast cancer in southern Taiwan

In this study, the genetic polymorphisms associated with breast cancer in southern Taiwan were investigated. Two categories of genes were analyzed: (1) BRCA1, BRCA2, and Rad51, the DNA repair factors involved in homologous recombinational repair; and (2) CYP1A1, COMT, GST, and NAT2, the xenobiotic-metabolizing enzymes (XME) involved in estrogen metabolism. We found that the number of deletions and/or mutations in the GST genes was highly correlated with the occurrence of breast cancer. These data suggest that the GST enzymes, which detoxify the catechol estrogen quinones, are important target molecules for screening in populations at high risk of breast cancer.     

The contribution of inherited factors to the clinicopathological features and behavior of breast cancer

This review is focused on genetic factors that may influence the development and/or appearance of breast cancer metastases. Over the last decade there have been significant advances in the understanding of genetic predisposition to breast cancer. The first breast cancer predisposing gene to be identified was TP53, and this was followed over the next 5 years by two more genes, BRCA1 and BRCA2, which from a population perspective are much more important than TP53. Other rarer genes have subsequently been identified, but the role of more common, less penetrant genes in breast cancer susceptibility remains unknown. Recent work has shown that breast cancers occurring in women carrying germ-line BRCA1 mutations tend to have clinicopathological features that are usually associated with a poor prognosis, such as high grade, estrogen receptor negative status and somatic TP53 mutations. On the other hand, they are usually ERBB2 negative. Whether or not such tumors are more or less likely to metastasize, and hence be associated with a poor outcome, is currently uncertain and has been the subject of much debate. Here, we outline some of the clinicopathological features of hereditary breast cancer, discuss the prognostic studies that have been performed, and introduce some possible new research directions.     

Breast cancer in women at high risk: The role of rapid genetic testing for BRCA1 and -2 mutations and the consequences for treatment strategies

Specific clinical questions rise when patients, who are diagnosed with breast cancer, are at risk of carrying a mutation in BRCA1 and -2 gene due to a strong family history or young age at diagnosis. These questions concern topics such as 1. Timing of genetic counseling and testing, 2. Choices to be made for BRCA1 or -2 mutation carriers in local treatment, contralateral treatment, (neo)adjuvant systemic therapy, and 3. The psychological effects of rapid testing. The knowledge of the genetic status might have several advantages for the patient in treatment planning, such as the choice whether or not to undergo mastectomy and/or prophylactic contralateral mastectomy. The increased risk of developing a second breast cancer in the ipsilateral breast in mutation carriers, is only slightly higher after primary cancer treatment, than in the general population. Prophylactic contralateral mastectomy provides a substantial reduction of contralateral breast cancer, although only a small breast cancer specific survival benefit. Patients should be enrolled in clinical trials to investigate (neo)-adjuvant drug regimens, that based on preclinical and early clinical evidence might be targeting the homologous recombination defect, such as platinum compounds and PARP inhibitors. If rapid testing is performed, the patient can make a well-balanced decision. Although rapid genetic counseling and testing might cause some distress, most women reported this approach to be worthwhile. In this review the literature regarding these topics is evaluated. Answers and suggestions, useful in clinical practice are discussed.     

Elevated plasma thymosin-α1 levels in lung cancer patients

Objective: Prothymosin-α, the precursor of thymosin-α1, may play a role in cell proliferation, and the plasma level of thymosin-α1 may reflect the degree of proliferation of the tumor cells. Methods: Recently, a new sandwich immunoradiometric assay for thymosin-α1 was developed using monoclonal and polyclonal antibodies. In this investigation, we used this assay to measure plasma and tissue level of thymosin-α1 in 131 lung cancer patients. Results: We found that the mean plasma thymosin-α1 levels in lung cancer patients were higher than in normal individuals (P<0.001). However, half of the patients showed normal levels. Thymosin-α1 levels correlated neither with the stage nor pathological subtype of the lung cancer, and did not decrease significantly in the 4 weeks after the resection of the tumor. Thymosin-α1 levels of lung cancer patients with another cancer were higher than those without evidence of other cancers (P=0.03). Survival of patients with normal levels of plasma thymosin-α1 was significantly better than that with higher levels (P=0.04). Conclusions: The plasma level of thymosin-α1 may be used as a marker for the prognosis of lung cancer patients. Further investigations are warranted to determine its role in the lung cancer.     

Heterogenic Loss of the Wild-Type BRCA Allele in Human Breast Tumorigenesis

Background For individuals genetically predisposed to breast and ovarian cancer through inheritance of a mutant BRCA allele, somatic loss of heterozygosity affecting the wild-type allele is considered obligatory for cancer initiation and/or progression. However, several lines of evidence suggest that phenotypic effects may result from BRCA haploinsufficiency. Methods Archival fixed and embedded tissue specimens from women with germ line deleterious mutations in BRCA1 or BRCA2 were identified. After pathologic review, focal areas of normal breast epithelium, atypical ductal hyperplasia, ductal carcinoma-in-situ, and invasive ductal carcinoma were identified from 14 BRCA1-linked and 9 BRCA2-linked breast cancers. Ten BRCA-linked prophylactic mastectomy specimens and 12 BRCA-linked invasive ovarian carcinomas were also studied. Laser catapult microdissection was used to isolate cells from the various pathologic lesions and corresponding normal tissues. After DNA isolation, real-time polymerase chain reaction assays were used to quantitate the proportion of wild-type to mutant BRCA alleles in each tissue sample. Results Quantitative allelotyping of microdissected cells revealed a high level of heterogeneity in loss of heterozygosity within and between preinvasive lesions and invasive cancers from BRCA1 and BRCA2 heterozygotes with breast cancer. In contrast, all BRCA-associated ovarian cancers displayed complete loss of the wild-type BRCA allele. Conclusions These data suggest that loss of the wild-type BRCA allele is not required for BRCA-linked breast tumorigenesis, which would have important implications for the genetic mechanism of BRCA tumor suppression and for the clinical management of this patient population.