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

Emma Edwards Æ Catharina Yearwood ÆJulie Sillibourne Æ Diana Baralle Æ Diana Eccles

Published online: 21 July 2009

� Springer Science+Business Media B.V. 2009

Abstract 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.

Keywords BRCA1 � Familial breast cancer �De novo mutation

Abbreviations

BIC Breast Cancer Information Core

CSCE Conformation sensitive capillary electrophoresis

dHPLC Denaturing high performance liquid

chromatography

ER? Oestrogen receptor positive

HER2 Human epidermal growth factor receptor 2

Introduction

Genetic testing for BRCA1 and BRCA2 has been available

since 1994, and in recent years has become more accessi-

ble. Comprehensive testing for mutations throughout the

coding sequence of both genes is now widely available and

should include a search for rearrangements, whole exonic

deletions and duplications. While the Breast Cancer

Information Core (BIC) Database is not complete, it holds

the largest record of reported BRCA1 and BRCA2 muta-

tions. To date over 1590 distinct genetic variants including

deleterious mutations, polymorphisms and unclassified

variant have been reported in BRCA1 and 1856 in BRCA2

(BIC Database 14/08/2008). The stronger the family his-

tory, the higher the likelihood of finding a mutation and the

more cost effective is screening. In the United Kingdom

the National Institute for Clinical Excellence recommends

that genetic testing for BRCA1/2 is considered if the like-

lihood of detecting a BRCA1 or BRCA2 mutation is better

than 20% [1]. Estimates of likelihood are based on indi-

vidual and family history information and it is very difficult

for an isolated individual with cancer to exceed that limit.

Mutation screening of unselected patients is not recom-

mended due to the low detection rate [2–5]. Research

performed on the UK population suggests that 3.6–5.3% of

young onset breast cancer without a family history is due to

a mutation in either BRCA1 or BRCA2 [6, 7]. This means

that up to 6% of mutations will be missed if Clinical

Genetics Services rely on the current guidelines. Several

methods exist to help determine an individual’s eligibility

for genetic testing. Families with three or more cases

of breast cancer on the same side of the family, who do

not have a probability greater than 20% of finding a

BRCA1 or BRCA2 mutation are invited to take part in a

research study, UK Familial Breast Cancer Study (Chief

Prof Nazneen Rahman, UK Familial Breast Cancer Study, Section of

Cancer Genetics, Institute of Cancer Research, 15 Cotswold Rd,

Sutton, Surrey, SM2 5NG

The Breast Cancer Information Core (BIC) Database

http://www.nhgri.nih.gov/Intramural_research/Lab_transfer/Bic/

Member/index.html

E. Edwards (&) � D. Baralle � D. Eccles

Wessex Clinical Genetics Service, Princess Anne Hospital,

Level G, Mailpoint 105, Coxford Road, Southampton,

Hampshire SO16 5YA, UK

e-mail: Emma.Edwards@suht.swest.nhs.uk

C. Yearwood

Molecular Genetics Diagnostics Laboratory, St Georges

Hospital, London, UK

J. Sillibourne

Wessex Regional Genetics Laboratory, Salisbury, UK

123

Familial Cancer (2009) 8:479–482

DOI 10.1007/s10689-009-9270-8

Investigator Prof Nazneen Rahman). This study screens for

BRCA1 and BRCA2 mutations as part of their recruitment

procedure to eliminate families who carry one of these

mutations before including families in studies to identify

other breast cancer susceptibility genes.

De novo mutations are reported frequently in several

genetic conditions caused by dominantly inherited gene

faults in large genes, such as NF1 [8, 9] and Fibrillin [10,

11]. However, only three proven de novo BRCA mutations

have been reported to date in the worldwide literature

[12–14]. Whilst de novo mutations are very likely to occur,

the complexities of mutation testing and being able to

access both parents for testing means that the true pro-

portion of de novo BRCA1 or BRCA2 mutation carriers

amongst isolated cancer cases is unknown.

Case study

We report a 44-year old lady referred to the Clinical

Genetics Service following her diagnosis of young onset

bilateral breast cancer. At 38 she was diagnosed with a

30 mm oestrogen receptor positive (ER?), Grade 2, infil-

trating ductal carcinoma of the left breast with foci of high

grade ductal carcinoma in situ and some cancerisation of

the lobules. She was treated with chemotherapy, radio-

therapy and Tamoxifen. This was followed by a 4.5 mm

Grade 3 infiltrating ductal carcinoma of the right breast at

43, which was oestrogen and progesterone receptor posi-

tive. She was again treated with chemotherapy and radio-

therapy followed by Arimadex. She gave a family history

of a maternal aunt confirmed to have had breast cancer

prior to her death at 54 years. The rest of the family history

was unremarkable (see Fig. 1).

This family scored 9 on the Manchester Score [15] and

had a combined BRCAPRO calculation [16] of 0.149

(BRCA1 = 0.022, BRCA2 = 0.127). The proband was not

eligible for genetic testing of BRCA1/2 genes through the

diagnostic laboratory. However, she was eligible for the

UK Familial Breast Cancer Study and was recruited.

BRCA1 and BRCA2 screening using CSCE revealed a

BRCA1 mutation (BRCA1_c.5332?1g[a in intron 21)

predicted to abolish the splice donor site for exon 21. This

is highly likely to be associated with an increased risk of

cancer. A fresh DNA sample was sent to Wessex Regional

Genetics Laboratory who confirmed this result in the

diagnostic laboratory. The splice site prediction program

(www.fruitfly.org) confirms this mutation is likely to cause

aberrant splicing and is highly likely to be disease causing.

Testing of both parents was offered so that the correct

side of the family could be informed of this result. Due to

the maternal family history, the proband’s mother was

assumed to be the most likely candidate to have the gene

fault. Genetic testing was carried out on both parents and

neither was shown to carry the BRCA1 mutation. The

proband’s sister also had predictive testing and does not

carry the mutation.

BRCA1 Exon 21 was sequenced using intronic primers

in duplicate from samples from the proband and her

parents and then re-sequenced using alternative intronic

primers, which confirmed that no mutation was present in

either parent. Assigning correct paternity in particular can

be an issue in genetic testing so Powerplex identity

testing was performed. This confirmed that parentage of

the proband was as stated and confirmed that the BRCA1

mutation had arisen de novo in the proband. All familial

samples received along with normal controls were run

using dHPLC and CSCE for the exon 21 fragment, which

includes the exon 21 splice donor site. There was a clear

shift in DNA from the proband, while the rest of the

family were normal, indicating no sign of somatic

mosaicism in either parent.

Fig. 1 Family pedigree

480 E. Edwards et al.

123

Discussion

The likelihood of finding a BRCA1 or BRCA2 mutation in

an individual depends on personal and family history and

the sensitivity of the molecular tests used. For series of

isolated young onset cases reported mutation detection

rates have risen from 3–6% in some series reported in the

1990s to 9–17% for more recent series [6, 7, 17–27]. With

new advancements in techniques used to identify muta-

tions, the contribution of BRCA1/2 to early onset breast

cancer may now be slightly higher than these reports.

In the United Kingdom up to 6% of BRCA1 and BRCA2

cases are likely to be missed by not testing individuals due

to a lack of family history. Lack of family history may relate

to small family size, non-penetrance, premature death, loss

of contact with family members and inadequacy of the

information about the family history or because of de novo

mutations in BRCA1 and BRCA2. There are three previ-

ously reported de novo mutations in BRCA from Australia,

USA and the Netherlands. Tesoriero et al. [12] report a

woman with early onset breast cancer who was found to

have a BRCA1 c.3769_3770delGA (previously 3888delGA)

and BRCA2 c.5946delT (previously 6174delT). The BRCA2

mutation was inherited from her father, but neither parent

carried the BRCA1 c.3769_3770delGA mutation. This

mutation has been reported twice on the BIC database and is

a truncating mutation. Robson et al. [14] were the first to

report a unique de novo mutation in BRCA2 at c.7032dupA

(previously 7260insA). This mutation results in a stop at

codon 2358. Van der Luijt et al. [13] reported a woman with

early onset breast cancer who was found to have a BRCA2

germline mutation at c.2806_2809delAAAC (previously

3034del4). Again molecular testing proved this to be de

novo. Unlike the other two reports, this mutation has been

recorded 23 times in the BIC database and results in a stop

at codon 959.

Along with our report, these three reported cases of de

novo mutations suggest that guidelines need to be re-

examined as these studies underline the importance of

mutation screening of the BRCA1 and BRCA2 genes in

patients with early onset breast cancer without a family

history. While the chance of finding a mutation is low, speed

and ease of testing is reducing the cost and time for results.

Tumour pathology may give clues to an underlying

mutation. In BRCA1, tumours are typically oestrogen,

progesterone and HER2 negative [28]. In the case pre-

sented here BRCA2 would have been predicted to be the

more likely but this case illustrates that tumour pathology

and immunohistochemical profile can be used to weight

likelihood, but cannot absolutely exclude the chance of a

hereditary mutation.

Finding an underlying genetic predisposition to breast

cancer is important as clinical management may be

significantly influenced by the information obtained by

genetic testing. If there is no family history, a negative

mutation screen significantly reduces the risk of ovarian

cancer. However, if a mutation is identified women can be

advised of their risks and may choose to have prophylactic

bilateral salpingo-oophorectomy. This will reduce the

chance of ovarian cancer, reduce the risk of breast cancer

recurrence (in ER? disease) and reduce the future risk of a

new primary breast cancer. Women may also wish to

consider risk-reducing mastectomy if they are identified as

a gene carrier. Due to these significant clinical implications

for the affected woman and her family, consideration

should be given to genetic testing women with early onset

breast cancer who do not have a family history, especially

where tumours are high grade and bilateral.

Acknowledgements All laboratory work was carried out at Wessex

Regional Genetics Laboratory. Catharina Yearwood has subsequently

moved to St George’s Hospital.

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