Homozygosity of MSH2 c.1906G?C germline mutationis associated with childhood colon cancer, astrocytomaand signs of Neurofibromatosis type I

Helen Toledano Æ Yael Goldberg Æ Inbal Kedar-Barnes Æ Hagit Baris ÆRinnat M. Porat Æ Chen Shochat Æ Dani Bercovich Æ Eli Pikarsky ÆIsraela Lerer Æ Isaac Yaniv Æ Dvorah Abeliovich Æ Tamar Peretz

Published online: 20 December 2008

� Springer Science+Business Media B.V. 2008

Abstract Hereditary non-polyposis colorectal cancer is a

cancer predisposition syndrome known to be caused by

heterozygous germline mutations in DNA mismatch repair

genes (MMR) most commonly hMLH1, hMSH2, hMSH6.

Heterozygous mutations in one of these genes confer an

increased risk, mainly for colon and endometrial cancer.

Recently, several publications identified that biallelic

mutations in the MMR genes are associated with a more

severe phenotype, including childhood malignancies and

signs of neurofibromatosis type I (NF1). We report on a non-

consanguineous Ashkenazi Jewish family with two affected

siblings with features of NF1, colon cancer and astrocytoma

at age 13 and 14. Their mother developed endometrial

cancer at age 54. Their father had leukoplakia of the vocal

cords with a family history of pancreatic cancer. Molecular

and pathology studies were done on the tumor tissue and on

genomic DNA of family members. Tumor testing demon-

strated a high degree of microsatellite instability (MSI

analysis), expression of MLH1 and absence of expression of

both MSH2 and MSH6 proteins. A biallelic c.1906G [ C

(p.A636P) mutation in the hMSH2 gene was detected in the

blood of one affected child. Parental genetic testing showed

that each parent was heterozygote for the mutation. The

c.1906G [ C mutation is a founder mutation in the Ashke-

nazi Jewish population. To our knowledge this is the first

report of homozygosity for this founder mutation.

Keywords HNPCC, NF1 � Ashkenazi � Bi-allelic �MMR � MSI � MSH2

Abbreviations

AC Amsterdam criteria

CCS Childhood cancer syndrome

CRC Colorectal cancer

DHPLC Denaturing high performance liquid

chromatography

HNPCC Hereditary non-polyposis colorectal cancer

IHC Immunohistochemistry

MLPA Multiplex ligase dependent probe amplification

MMR Mismatch repair

MMR-

D

Mismatch repair deficiency

MSI Microsatellite instability

NF1 Neurofibromatosis type 1

H. Toledano and Y. Goldberg contributed equally to the paper.

H. Toledano � I. Yaniv

Schneider Children’s Medical Center of Israel and Sackler

Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel

Y. Goldberg (&) � T. Peretz

Sharett Institute of Oncology, Hadassah-Hebrew University

Medical Center, P.O. Box 12000, 91120 Jerusalem, Israel

e-mail: yaelg@hadassah.org.il

I. Kedar-Barnes � H. Baris

The Raphael Recanati Genetic Institute Rabin Medical Center,

Beilinson Hospital, Petah Tikva, Israel

R. M. Porat � E. Pikarsky

Department of Pathology, Hadassah-Hebrew University Medical

Center, Jerusalem, Israel

C. Shochat � D. Bercovich

The Human Molecular Genetics & Pharmacogenetics lab,

Migal - Galilee Bio-Technology Center, Kiryat-Shmona, Israel

I. Lerer � D. Abeliovich

Department of Human Genetics, Hadassah-Hebrew University

Medical Center, Jerusalem, Israel

D. Bercovich

Tel Hai Academic College, Tel Hai, Israel

123

Familial Cancer (2009) 8:187–194

DOI 10.1007/s10689-008-9227-3

Introduction

Hereditary non-polyposis colorectal cancer (HNPCC) is an

autosomal dominant inherited condition known to be

associated with a predisposition to several malignancies,

mainly colorectal cancer (CRC) and endometrial cancer.

Other malignancies such as ovarian, gastric, small intes-

tine, pancreas, bile duct, urinary tract and brain tumors

have also been associated with HNPCC [1, 2]. Typically,

affected individuals with HNPCC present with cancer in

the fourth or fifth decade but in some families the pre-

sentation may be in the third decade or later in the sixth

decade [2]. Germline and somatic mutations in the MMR

genes have been implicated in HNPCC and in 15–20% of

sporadic CRC [1, 3]. In HNPCC, defined by the presence of

a MMR gene mutation, mutations in hMLH1 and hMSH2

account for approximately 90% of cases, hMSH6 for 10%

and hPMS2 accounts for less than 5% [4].

Biallelic mutations in the MMR genes lead to a dis-

tinctive syndrome, characterized by hematological

malignancies, tumors of brain and bowel early in child-

hood, often associated with signs of neurofibromatosis type

1 (NF1). This syndrome has been referred to as childhood

cancer syndrome (CCS) [5] and mismatch repair deficiency

syndrome (MMR-D) [6]. In 1999, Wang et al. were the first

to describe the association between compound heterozy-

gous mutation in MLH1 gene, early onset extracolonic

cancers and signs of NF1 [7]. Menko et al. described a

child with multiple cafe-au-lait spots (CLS), oligodendro-

glioma and rectal cancer who was homozygous for a

mutation in hMSH6 gene [8]. Kruger et al. [9] reported on

six children from two consanguineous families with a

homozygous PMS2 mutation, who suffered from glioblas-

toma, colorectal cancer, lymphoma and other HNPCC-

associated tumors at early ages. Kruger et al. also reviewed

reports of 43 individuals with biallelic MMR germline

mutations in 23 different families. Brain tumors occurred in

most families, followed by hematological malignancies and

intestinal tumors [9]. All affected individuals with CCS had

clinical features characteristic of NF1: either CLS, or CLS

and axillary freckling. The median age of tumor onset was

9 years, ranging from 1 to 24 years.

Mouse knockouts for all MMR genes have been gen-

erated [10–12]. When comparing the tumor spectra of these

homozygous mouse models to the spectrum of humans

with biallelic mutations it becomes clear that they are

similar in terms of frequent lymphoma development and

relatively low abundance of gastrointestinal tumors. A

difference is that brain tumors are very rare and neurofi-

bromas and CLS are absent in mouse MMR knockouts. In

Msh2 deficient mice there is an increasing rate of somatic

mutations in genes associated with tumorigenesis [13].

Knockout mutants of the three major MMR genes in

zebrafish mimic distinct features of the human disease and

are complementary to mouse models. They develop pre-

dominantly, neurofibromas/malignant peripheral nerve

sheath tumors at low frequencies [14].

Several mutations in HNPCC have been described as

founder mutations in certain populations; two founder

mutations in the MLH1 gene account for 63% of all dele-

terious mutations identified in HNPCC families in the

Finnish population [15]. The MSH2 c.1906G [ C mutation

was initially described by Yuan et al. in an Ashkenazi

Jewish family that fulfilled the Amsterdam criteria for the

clinical diagnosis of HNPCC [16]. This finding was con-

firmed by Foulkes et al. [17]. The mutation results in a

substitution of alanine to proline at codon 636 (A636P) in

the MSH2 protein, associated with an alteration in MSH2

Crystal structure. Foulkes et al. [17] found that all CRC

tumors, from carriers of the mutation, were MSI-H and

were negative for the expression of both MSH2 and MSH6

proteins in all tumors examined by IHC studies. This

finding could be explained by the fact that MSH2 and

MSH6 form a functional complex-MutSa, as a result

MSH2 loss often causes concurrent loss of MSH6.

The MSH2 c.1906G [ C mutation was examined in a

population-based series of Ashkenazi Jews with colorectal

cancer and shown to be rare (0.44%), yet highly penetrant;

In a combined consecutive series from Israel, New York

and Toronto, the A636P mutation was found in 8 of 1,345

(0.59%) Ashkenazi Jewish CRC cases versus 0 of 1,588

healthy Ashkenazi Jewish controls [17]. It has been

reported that 20–30% of Ashkenazi Jewish families that

fulfill Amsterdam criteria carry this mutation [18, 19].

Hereby, we describe a family with two siblings who

died from cancer in childhood. One was affected with

features of NF1 and astrocytoma and the other sibling with

features of NF1, astrocytoma and CRC. Genetic studies for

HNPCC done on one sibling found that he was homozy-

gous for a c.1906G [ C (A636P) mutation in the MSH2

gene. Both parents were found to be heterozygous for the

mutation. None of them come from a family that complies

with the Amsterdam Criteria, or fulfills the Bethesda

guidelines.

Materials and methods

Patient data

The proband, a 14-year-old boy, presented with a two-

month history of fatigue, mild weight loss, falls, intermit-

tent melena and fresh blood per rectum. A blood count

revealed hemoglobin of 7.7 g/dl with microcytic indices.

Past history was remarkable for the fact that since child-

hood he had been noted to have multiple CLS on the skin.

188 H. Toledano et al.

123

He was presumed to have NF1 and had been seen inter-

mittently in an NF clinic. Brain MRI studies 2 years earlier

reportedly showed changes in the temporal region consis-

tent with the diagnosis of NF1. On examination at the

pediatric day center he appeared pale, thin and unwell. He

had torticollis and ataxia.

A family history of a brother who had died of a

malignant brain tumor was reported. The clinical exami-

nation and his family history prompted an immediate MRI

of the brain which revealed two separate lesions. One was

in the temporal area—this had been present on the MRI

from 2 years previously but was considerably enlarged and

the other was a large lesion in the pons with an appearance

of a diffuse brainstem glioma that had not been evident on

the previous MRI (Fig. 1a). He underwent resection of the

temporal lesion only and pathology revealed a fibrillary

astrocytoma (grade II).

He then had a gastrointestinal workup for the anemia,

which included an upper GI endoscopy and a barium study

of the small bowel that were reported as normal. However,

colonoscopy revealed a large mass in the rectum 3 cm from

the anal sphincter and there were 20–30 polyps throughout

the large bowel of different sizes and biopsies were taken.

Pathology revealed the polyps to be tubulo-villous adeno-

mata and the rectal mass was a well differentiated

adenocarcinoma. Tumor markers CEA and CA19-9 were

normal. MRI demonstrated involvement of the peri-rectal

fat and PET-CT showed uptake in the mass and several of

the polyps but not in the lymph nodes and there was no

evidence of distant metastases.

In view of the average 1 year life expectancy following

diagnosis of a brain stem glioma there was debate

regarding the management of the rectal tumor. However,

longer than average survival has been described for glio-

mas in some genetic conditions such as Turcot syndrome

and after discussion with the family it was decided to start

aggressive management of his rectal tumor. Since imme-

diate surgery for the rectal mass would have involved

permanent loss of sphincter function, initial chemo-radia-

tion with the hope of shrinking the tumor and performing

sphincter-sparing surgery at a later date was attempted. At

the same time, he began suffering from increasing right-

sided weakness and falls and MRI showed increased size of

the brain stem lesion so that he received radiation therapy

simultaneously to the brain and rectum. Imaging studies

performed 6 weeks after completion of radiation showed

an improvement in the brain lesion but increase in size of

the rectal mass, making sphincter sparing surgery impos-

sible. Since colonic polyposis is a premalignant condition

and some of his polyps were already large and positive on

the PET scan he underwent panproctocolectomy with

permanent ileostomy. Pathology confirmed adenocarci-

noma of the rectum without lymph node involvement and

approximately 100 polyps in the large bowel.

Post-operatively he received adjuvant chemotherapy for

the rectal tumor with the FOLFOX regimen but had early

relapse at the rectal stump 2 months post-operatively. He

received second line therapy with FOLFIRI and Avastin

but by 11 months post diagnosis he was suffering from

intractable rectal pain as well as neurological deterioration

and he died at 1 year following the diagnosis.

At the time of his diagnosis with two concurrent tumors

and the death of their previous son, increasing family anxiety

prompted referral to genetic counseling. Physical examina-

tion by the geneticist revealed: head circumference 51 cm

(\2%), multiple CLS scattered over the body of which 21

were between 15 and 55 mm in diameter and multiple

smaller spots. There was inguinal and axillary freckling.

Asymmetrical facies (right [ left) was evident. Neurologi-

cal examination was normal except for mild imbalance

exhibited on tandem walk test only. Ophthalmological

evaluation excluded Lisch nodules but bilateral retinal

Fig. 1 MRI of brain tumor. a MR T2 weighted sagittal image of the

brain at diagnosis. Hyperintensity of the pons and medulla is seen,

compatible with a brain stem tumor. b, c MR T1 weighted fat

suppressed axial image of the lower pelvis post Gadolinium injection.

b At diagnosis: irregular thickening of the rectal wall is seen,

indicative of tumoral involvement. 10 months post diagnosis. c Local

recurrence is evident: a large necrotic mass is seen between the

sacrum and the bladder

Homozygosity of MSH2 c.1906G?C Ashkenazi mutation 189

123

hyperpigmentation raised the possibility of congenital

hypertrophy of the retinal pigment epithelium (CHRPE).

Targeted physical examination of his family members

included paternal head circumference of 54.4 cm (25%),

maternal head circumference of 52 cm (2%). No CLS were

observed on his father’s and mother’s dermal examination.

His healthy siblings had one CLS each.

Family history

The proband was the youngest of four siblings: two

apparently healthy siblings and another brother who was

diagnosed with anaplastic astrocytoma and NF1 features

and died at the age of 13. During the proband’s treatment

his father received radiation for severe, progressive lar-

yngeal leukoplakia and his mother was diagnosed age 54

with endometrial carcinoma and underwent a hysterec-

tomy. A paternal grandfather had been diagnosed with

pancreatic cancer at age 61 and died soon after. All living

first-degree relatives had a colonoscopy that was reported

as normal (Fig. 2).

Tumor testing

Tumor tissue was obtained from archived paraffin blocks.

Normal and pathological tissue of the colon were differen-

tially marked on the slide. DNA extraction from the paraffin

embedded tissues was performed as described [20]. DNA

was extracted from peripheral blood lymphocytes using the

QIAGEN DNA Isolation kit (QIAGEN, Germany).

MSI analysis was performed by a fluorescence-based

PCR method as described [21]. PCR products were ana-

lyzed on ABI Sequencer (3100) using GeneScan and

Genotyper software (PE Applied Biosystems).

Immunohistochemistry analysis

Five micro meter paraffin sections were de-waxed and

hydrated through graded ethanols, antigen retrieval was

done either with 20 mM citrate buffer pH 6.0 (hMSH2) or

with Borg Decloaker (Biocare Medical) pH 9.5 (hMLH1

and hMSH6) in a pressure cooker (Biocare Medical).

Slides were incubated with the indicated primary antibody,

diluted 1:50 in CAS-Block (Zymed) for overnight at 48C,

washed with Optimax (biogenex), incubated with MACH 3

Mouse HRP Polymer (Biocare Medical) and developed

with DAB. Normal cells showing strong nuclear staining

for the MMR proteins were used as an internal positive

control. Mouse monoclonal antibodies used were: hMLH1:

clone G168-15; hMSH2: clone FE11; hMSH6: clone BC/

44 from Biocare Medical.

DHPLC homozygous mutations screening

Mutation testing of the MMR genes was performed using a

combination of DHPLC and semiquantitative fluorescent

multiplex–PCR analysis. To identify homozygous muta-

tions, 10 ll PCR product of wild-type DNA, and 10 ll

PCR product of sample DNA were mixed 1:1 and dena-

tured at 95�C. This enabled detection of homozygous

Fig. 2 An abbreviated pedigree

of the reported family: Squaresmales; circles females; diagonalbars deceased; black mini-squares cancer; MSH2/

MSH2—homozygous for the

c.1906C [ G mutation;

w/w—wild-type for mutation;

w/MSH2 heterozygous for

mutation

190 H. Toledano et al.

123

mutations by formation of a heteroduplex [22]. All exonic

fragments of each gene, including intron junctions, were

amplified individually. PCR and DHPLC (WAVE, Trans-

genomic Inc., Omaha, NE) were preformed as described

previously [18, 23].

Testing for the Ashkenazi Jewish mutation

The c.1906G [ C was tested by allele specific amplifica-

tion as described in [18]. PCR conditions: 94�C—20 min;

35 cycles of 94�C—30 s; 61�C—1 min; 72�C—1 min;

final extension 20 min—72�C. PCR products run on 3%

NuSieve-Agarose gel (FMC-CAMBREX) in TBE buffer,

stained with ethidium bromide and visualized under UV

illumination.

Results

Tumor analysis

IHC

Immunostaining with antibodies against MLH1, MSH2 and

MSH6 was performed on tumor samples derived from the

proband, 14-year-old boy and from the mother. Immuno-

staining of the adenocarcinoma of the rectum from the

14-year-old patient shows nuclear staining for MLH1 both

in the tumor and in the normal cells (Fig. 3a) indicating the

retained protein, whereas the adenocarcinoma cells show

loss of nuclear staining for MSH2 and MSH6 (Fig. 3b, c).

Interestingly, the normal cells were also devoid of nuclear

staining for MSH2. The mother’s endometrial adenocar-

cinoma showed a similar pattern of loss of MSH2 and

MSH6 staining, with retained MLH1 staining as demon-

strated in Fig. 3d–i.

MSI (child, mother)

both tumors showed high degree of MSI in DNA extracted

from tumor tissue (Fig. 4) and showed microsatellite sta-

bility in DNA extracted from peripheral leukocytes, as

shown in Fig. 4. As can be seen, no difference in the pat-

tern of stability was seen between the heterozygote and the

homozygote samples.

Molecular analysis

Based on the results obtained from tumor testing, we tested

DNA from peripheral leukocytes. Genetic studies on the

Fig. 3 Immunostaining with antibodies against MLH1, MSH2 and

MSH6: Positive staining with antibodies against MSH2 and MSH6 is

represented by the presence of nuclear brown staining. Thick arrowsindicate tumor cells. Arrow heads indicate internal positive control

cells, either stromal or epithelial. Sections of moderately differentiated

adenocarcinoma of the rectum (a–c) show retained nuclear staining for

MLH1 (a) and loss of MSH2 and MSH6 staining (b, c). Endometrial

tissue with positive MLH1 staining in normal (d) and tumor cells (e) but

negative MSH2 and MSH6 staining in tumor nuclei (g, i)

Homozygosity of MSH2 c.1906G?C Ashkenazi mutation 191

123

proband revealed a homozygous c.1906G [ C germline

mutation in the hMSH2 gene (Fig. 5). Both parents were

found to be carriers of a heterozygous mutation. The pro-

band’s sister did not carry the mutation and a living brother

was found to be a healthy carrier for the mutation (Fig. 2).

Discussion

We report two siblings from a non-consanguinous Ashkenazi

family who present with CCS due to biallelic inheritance of

the Ashkenazi c.1906G [ C founder mutation in the MSH2

gene. Both had features of NF1, one died from Astrocytoma,

and the other had colon cancer and Astrocytoma at age 13 and

14, respectively. Their mother developed endometrial cancer

at age 54. Their father had leukoplakia of the vocal cords with

a family history of pancreatic cancer. Neither of the parental

families fulfilled the Amsterdam Criteria.

In contrast to the well-known phenotype caused by

heterozygous MMR gene mutations, little is known about

the phenotype of the very rare biallelic MMR mutation

carriers. Until recently, less than 100 carriers with biallelic

Fig. 4 DHPLC and direct sequencing of the homozygote son and

heterozygote mother. Screening for mutations in the MSH2 gene by

the DHPLC and direct sequencing of PCR fragments with abnormal

chromatograms in comparison to wild-type demonstrates the exis-

tence of a homozygous mutation (A636P). a, b The homozygous

mutation (son) was detected by mixing the patient PCR products with

a wild-type PCR (1:1) before denaturation and reaniling (b). cHeterozygous DNA (mother) was detected by regular screening of

PCR products after denaturation and reaniling

Fig. 5 MSI analysis by the

BAT25 marker in peripheral

blood and tumor tissue from

heterozygote mother and

homozygous son. The pattern

of stability in the blood and the

pattern of instability in tumor

is similar

192 H. Toledano et al.

123

MMR germline mutations have been reported (reviewed in

[9]). Only two families with mutations in the MSH2 gene

were reported [24, 25]. To our knowledge there have been

no previous reports of homozygosity for the Ashkenazi

c.1906G [ C founder mutation in the MSH2 gene.

The clinical phenotype of the affected brothers raised

the diagnosis of CCS. However, given the clinical pre-

sentation of a brain tumor and multiple colonic polyps

([100) suggesting Turcot syndrome, a blood sample of the

proband was sent for sequencing of the APC gene.

Sequencing of exon 1–14 and 3,000 bases from the 50 of

exon 15 did not reveal any mutations (data not shown).

Though the proband presented with features of NF1, the

lack of suggestive family history and some features that did

not support this diagnosis (small head circumference, no

neurofibromas, and presence of multiple colonic polyps)

did not support this diagnosis. The age of onset of malig-

nancies, the presence of the features of NF1 in both siblings

and their absence in both parents, supported the diagnosis

of CCS, but the absence of a suggestive family history did

not corroborate the diagnosis. However, this is in line with

previous reports of biallelic MMR gene mutation carriers;

all had features of NF1, mostly multiple CLS, but seldom

fulfilled the NIH diagnostic criteria for NF1. Interestingly,

an absence of significant family history has been reported

in cases of CCS; Kruger et al. have already reported that

family history does not seem to be a good predictor for

identifying CCS, while the early onset of hematological

malignancies, brain or intestinal tumors together with signs

of NF1 identified CCS in 80% (20 out of 25) of families

with biallelic MMR gene germline mutation carriers [9].

It has been suggested that the NF1 gene is an early target

in embryogenesis of carriers of biallelic MMR gene

mutations. Puisieux reports that the NF1 gene appears to be

a preferential mutational target [26]. This is further sup-

ported by Wang et al. [27], showing a higher rate of

mutations in the NF1 gene in highly unstable human cell

lines and tumors, and in Mlh1 knockout mice compared to

MMR-sufficient tissue. Still, the link between these two

syndromes or the common features is yet to be clarified.

Patients carrying a homozygous deletion of an MMR

gene have a different spectrum of tumors than that of

heterozygotes; specifically, these patients have a higher

occurrence of nervous system tumors. While we cannot

definitely explain this different phenotype we would like to

suggest two possible explanations that should be further

explored: 1. The window of opportunity hypothesis—it is

possible that some tumors can only develop if the initiating

mutation occurs up to a certain time point in life. If this is

the case, than it is clear why homozygotes will be more

susceptible to such tumors. 2. The non-cell autonomous

effect hypothesis—it has been shown that mast cells

lacking one allele of NF1 play an important role in the

pathogenesis of plexiform neurofibromas in patients with

NF1 in a non-cell autonomous way through the secretion of

factors that facilitate the growth of tumor cells. It is possible

that in homozygotes for MMR genes the microenviron-

mental deficiency plays a similar role in the tumors unique

for this syndrome.

We identified MSI-H in the tumor tissues from the pro-

band and a stable pattern in leukocyte DNA. Stable pattern in

non-neoplastic cells is in line with other reports [28, 29] and

with some knockout models of the MMR genes. However,

some others report MSI in non tumoral cells [7] confirming

the constitutional defect in DNA MMR. It has been sug-

gested that the different results may be explained by the lack

of clonal populations in the peripheral blood sample, or

from the relative advantage of stable cells in the normal

tissue.

A characteristic phenomenon of HNPCC tumors is loss

of nuclear expression of MMR proteins detectable by

immunohistochemical procedures [30, 31]. Indeed, IHC for

MSH2 expression performed in both examined tumors,

(namely the proband’s colorectal tumor and the mother’s

endometrial adenocarcinoma), exhibited clear loss of

MSH2 expression (Fig. 3). Our results, that tumor cells

harboring the missense A636P mutation show absence of

MSH2 protein by immunohistochemical analysis, are in

agreement with the data reported by Foulks et al. [17].

While the correlation between the absence of MSH2

staining and the pathogenicity of the missense mutation is

notable, the fact that a single amino acid substitution in

MSH2 protein results in both distortion of the antigenic site

and MMR function loss may indicate that the mutated

protein is unstable. Testing recombinant MSH2-A636P

protein for MMR efficiency by in vitro assay showed a

complete loss of function [32]. A636 is a non-conserved

residue adjacent to a conserved region near the ATP-DNA

binding region. Therefore, another suggested explanation

for the functional loss is that an inflexible adenosine to

proline substitution may cause steric hindrance which not

only changes the antibody recognition site, but also alters

an otherwise conserved region in the protein and possibly,

interferes with its function.

The MSH2 c.1906G [ C mutation was shown to be

relatively rare among unselected Ashkenazi CRC patients,

yet highly penetrant [33]; surprisingly, none of the parental

families in our pedigree fulfilled the AC, and hardly

comply with the Bethesda guidelines. Of note, we and

others have previously reported few Ashkenazi families

with this mutation that also did not even comply with the

Bethesda guidleines [18].

The incidence of the c.1906G [ C founder mutation is

estimated to be very low in the Ashkenazi population.

Accordingly the chance of such an event to occur is very

rare. But, it is important that children, who have multiple

Homozygosity of MSH2 c.1906G?C Ashkenazi mutation 193

123

tumors and CLS, will be tested for the possibility of

biallelic MMR mutations [34]. One should be aware of the

occurrence of this syndrome also among non-consanguin-

eous families, given the presence of a founder mutation.

Acknowledgments This work was supported, in part, by the Israeli

Cancer Association, and by the Levinace Friedl foundation.

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