formalin - fixed , paraffin - embedded archival tissue samples from 100 patients who underwent complete surgical resection ( simpson grade i ) of meningiomas between august 2003 and december 2012 were collected from the databases of the department of pathology , seoul national university bundang hospital in korea .
two pathologists ( g.c . and s.y . ) independently reviewed the hematoxylin and eosin  stained slides , confirmed the diagnosis according to the 2007 who classification system , and classified the histological subtypes and grading of the meningiomas .
all the patients received regular follow - up after surgery , without postoperative chemoradiation therapy . the recurrence - free survival ( rfs )
evidence of tumor recurrence was provided by a computed tomography scan or a magnetic resonance image showing a meningioma in a location contiguous with the previous operation site .
the 100 patients consisted of 23 males ( 23% ) and 77 females ( 77% ) , with median age of 60 years ( range , 36 to 85 years ) . of these
, bone / soft tissue invasion was observed in 12 cases , brain invasion was observed in five cases , and both bone / soft tissue invasion and brain invasion were observed in one case .
we defined  soft tissue invasion  as invasion of the meningioma to the scalp or paranasal sinus . according to the 2007 who classification ,
histologically , the 100 cases consisted of meningothelial types ( n=32 ) , transitional types ( n=32 ) , fibrous types ( n=16 ) , angiomatous types ( n=13 ) , psammomatous types ( n=2 ) , microcystic types ( n=4 ) , and one metaplastic type ( n=1 ) ( table 1 ) .
we chose one representative tumor block in each case , and harvested cores with diameters of 3 mm from the most representative tumor areas of the donor blocks .
the cores were precisely arranged into new recipient tissue microarray ( tma ) blocks using a trephine apparatus according to previously described protocols .
briefly , sections of 4 m were transferred to poly - l - lysine coated adhesive slides and dried , deparaffinized , and rehydrated .
the following antibodies were used according to manufacturer instruction : c - met ( pre - dilution , rabbit monoclonal antibody , ventana medical systems , inc . , tucson , az , usa ) and hgf ( 1:100 , rabbit polyclonal antibody , santa cruz biotechnology , santa cruz , ca , usa ) .
the sections were incubated with appropriate reagents from the dako real envision detection system ( dako , glostrup , denmark ) , and were counterstained with mayer s hematoxylin .
evaluation of c - met and hgf expression was assessed according to previous reports . as a positive control for c - met and hgf , tubular cells of a normal
was categorized as positive when it showed moderate - to - strong cytoplasmic and/or membranous positivity in tumor cells .
accordingly , we scored expression as c - met and hgf ( > 25% positive cells ) and c - met and hgf ( 0%25% tumor cells ) ( fig .
the study was conducted according to the ethics standards of the world medical association s declaration of helsinki .
all statistical analyses were conducted using the spss ver . 21.0 ( ibm co. , armonk , ny , usa ) .
associations between the protein expressions of each antibody and the categorical variables were assessed using chi - square tests or fisher exact tests , if appropriate .
kaplan - meier survival curves for rfs were plotted for each antibody , and the survival comparison was determined using log rank tests .
formalin - fixed , paraffin - embedded archival tissue samples from 100 patients who underwent complete surgical resection ( simpson grade i ) of meningiomas between august 2003 and december 2012 were collected from the databases of the department of pathology , seoul national university bundang hospital in korea .
two pathologists ( g.c . and s.y . ) independently reviewed the hematoxylin and eosin  stained slides , confirmed the diagnosis according to the 2007 who classification system , and classified the histological subtypes and grading of the meningiomas .
all the patients received regular follow - up after surgery , without postoperative chemoradiation therapy . the recurrence - free survival ( rfs )
evidence of tumor recurrence was provided by a computed tomography scan or a magnetic resonance image showing a meningioma in a location contiguous with the previous operation site .
the 100 patients consisted of 23 males ( 23% ) and 77 females ( 77% ) , with median age of 60 years ( range , 36 to 85 years ) . of these
, bone / soft tissue invasion was observed in 12 cases , brain invasion was observed in five cases , and both bone / soft tissue invasion and brain invasion were observed in one case .
we defined  soft tissue invasion  as invasion of the meningioma to the scalp or paranasal sinus . according to the 2007 who classification , all were cases of benign meningiomas ( grade i ) .
histologically , the 100 cases consisted of meningothelial types ( n=32 ) , transitional types ( n=32 ) , fibrous types ( n=16 ) , angiomatous types ( n=13 ) , psammomatous types ( n=2 ) , microcystic types ( n=4 ) , and one metaplastic type ( n=1 ) ( table 1 ) .
we chose one representative tumor block in each case , and harvested cores with diameters of 3 mm from the most representative tumor areas of the donor blocks .
the cores were precisely arranged into new recipient tissue microarray ( tma ) blocks using a trephine apparatus according to previously described protocols .
briefly , sections of 4 m were transferred to poly - l - lysine coated adhesive slides and dried , deparaffinized , and rehydrated .
the following antibodies were used according to manufacturer instruction : c - met ( pre - dilution , rabbit monoclonal antibody , ventana medical systems , inc . ,
tucson , az , usa ) and hgf ( 1:100 , rabbit polyclonal antibody , santa cruz biotechnology , santa cruz , ca , usa ) .
the sections were incubated with appropriate reagents from the dako real envision detection system ( dako , glostrup , denmark ) , and were counterstained with mayer s hematoxylin .
evaluation of c - met and hgf expression was assessed according to previous reports . as a positive control for c - met and hgf , tubular cells of a normal kidney and normal colonic mucosa
was categorized as positive when it showed moderate - to - strong cytoplasmic and/or membranous positivity in tumor cells .
accordingly , we scored expression as c - met and hgf ( > 25% positive cells ) and c - met and hgf ( 0%25% tumor cells ) ( fig .
the study was conducted according to the ethics standards of the world medical association s declaration of helsinki .
all statistical analyses were conducted using the spss ver . 21.0 ( ibm co. , armonk , ny , usa ) .
associations between the protein expressions of each antibody and the categorical variables were assessed using chi - square tests or fisher exact tests , if appropriate .
kaplan - meier survival curves for rfs were plotted for each antibody , and the survival comparison was determined using log rank tests .
among the 100 cases of meningiomas , brain invasion was observed in five cases ( 5% ) . the median age of cases with brain invasion was 73 years ( range , 47 to 77 years ) .
additionally , 13% ( 3/23 ) of male patients presented with brain invasion , and 2.6% ( 2/77 ) of female patients presented with brain invasion . therefore , brain invasion was found to be more common in male patients . even in male patients , however , statistical significance was not reached ( p=.078 ) .
bone and/or soft tissue invasion was observed in 12 cases of meningiomas , consisting of two males ( 8.7% , 2/23 ) and 10 females ( 13% , 10/77 ) .
therefore , there was no significant association between bone / soft tissue invasion and sex ( p=.728 ) . the median age of patients with bone / soft tissue invasion was 58 years ( range , 42 to 75 years ) ( table 2 ) .
of the cases , c - met and hgf were found in 17% ( 17/100 ) and 13% ( 13/100 ) of meningiomas , respectively , and c - met / hgf co - expressions were observed in 1% ( 1/100 ) of meningiomas .
c - met and hgf showed no significant correlation with the histologic subtypes of meningiomas ( table 3 ) .
brain invasion was observed in 3/17 ( 17.6% ) of c - met meningiomas and in 2/83 ( 2.4% ) of c - met meningiomas .
therefore , there was a statistically significant correlation between c - met and brain invasion ( p=.033 ) .
neither hgf nor c - met / hgf co - expression showed statistical associations with brain invasion ( p=.375 and p=.562 , respectively ) ( table 4 ) .
of the cases , bone / soft tissue invasion was observed in 4/17 ( 23.5% ) of c - met meningiomas and in 8/83 ( 9.6% ) of c - met meningiomas .
there was a tendency for c - met meningiomas to show bone / soft tissue invasion more frequently than c - met meningiomas ; however , statistical significance was not reached ( p=.119 ) .
additionally , bone / soft tissue invasion was found in 15.4% ( 2/13 ) of hgf meningioma and 33.3% ( 2/6 ) of c - met / hgf meningioma . as a result , hgf and c - met / hgf co
- expressions did not show a significant association with bone / soft tissue invasion ( p=.653 and p=.151 , respectively ) . to identify whether the complete removal of meningiomas from patients differently impacts rfs periods
depending on the status of c - met and hgf expressions , we performed a univariate analysis of 100 cases of simpson grade i meningiomas . in the current study ,
the median follow - up period was 26.7 months ( range , 1.1 to 106.2 months ) .
c - met , two cases ( 11.8% ) ex - perienced recurrence , whereas two of 83 cases ( 2.4% ) with c - met suffered recurrence .
cases with c - met showed shorter rfs periods ( meanstandard deviation [ sd ] , 93.58.2 months ) than those of c - met ( meansd , 96.11.9 months ) ; however , statistical significance was not reached ( p=.139 ) .
hgf and c - met / hgf were not correlated with rfs according to our results ( fig .
among the 100 cases of meningiomas , brain invasion was observed in five cases ( 5% ) . the median age of cases with brain invasion was 73 years ( range , 47 to 77 years ) .
additionally , 13% ( 3/23 ) of male patients presented with brain invasion , and 2.6% ( 2/77 ) of female patients presented with brain invasion . therefore , brain invasion was found to be more common in male patients . even in male patients , however , statistical significance was not reached ( p=.078 ) .
bone and/or soft tissue invasion was observed in 12 cases of meningiomas , consisting of two males ( 8.7% , 2/23 ) and 10 females ( 13% , 10/77 ) .
therefore , there was no significant association between bone / soft tissue invasion and sex ( p=.728 ) . the median age of patients with bone / soft tissue invasion was 58 years ( range , 42 to 75 years ) ( table 2 ) .
of the cases , c - met and hgf were found in 17% ( 17/100 ) and 13% ( 13/100 ) of meningiomas , respectively , and c - met / hgf co - expressions were observed in 1% ( 1/100 ) of meningiomas .
c - met and hgf showed no significant correlation with the histologic subtypes of meningiomas ( table 3 ) .
brain invasion was observed in 3/17 ( 17.6% ) of c - met meningiomas and in 2/83 ( 2.4% ) of c - met meningiomas .
therefore , there was a statistically significant correlation between c - met and brain invasion ( p=.033 ) .
neither hgf nor c - met / hgf co - expression showed statistical associations with brain invasion ( p=.375 and p=.562 , respectively ) ( table 4 ) .
of the cases , bone / soft tissue invasion was observed in 4/17 ( 23.5% ) of c - met meningiomas and in 8/83 ( 9.6% ) of c - met meningiomas .
there was a tendency for c - met meningiomas to show bone / soft tissue invasion more frequently than c - met meningiomas ; however , statistical significance was not reached ( p=.119 ) .
additionally , bone / soft tissue invasion was found in 15.4% ( 2/13 ) of hgf meningioma and 33.3% ( 2/6 ) of c - met / hgf meningioma . as a result , hgf and c - met / hgf co
- expressions did not show a significant association with bone / soft tissue invasion ( p=.653 and p=.151 , respectively ) .
to identify whether the complete removal of meningiomas from patients differently impacts rfs periods depending on the status of c - met and hgf expressions , we performed a univariate analysis of 100 cases of simpson grade i meningiomas . in the current study ,
the median follow - up period was 26.7 months ( range , 1.1 to 106.2 months ) .
c - met , two cases ( 11.8% ) ex - perienced recurrence , whereas two of 83 cases ( 2.4% ) with c - met suffered recurrence .
cases with c - met showed shorter rfs periods ( meanstandard deviation [ sd ] , 93.58.2 months ) than those of c - met ( meansd , 96.11.9 months ) ; however , statistical significance was not reached ( p=.139 ) .
hgf and c - met / hgf were not correlated with rfs according to our results ( fig .
we set out to determinate whether the expression of c - met and hgf is associated with the invasiveness of meningiomas and their clinical implications . in the present study ,
c - met correlated with brain invasion and bone / soft tissue invasion . to the best of our knowledge ,
the protein known as c - met is a receptor tyrosine kinase ( rtk ) , and is a well - known proto - oncogene that is expressed in many organs , including the liver , pancreas , and prostate . in development and wound tissue , c - met
hgf is the known ligand of the c - met rtk [ 13 - 15 ] .
previous studies demonstrate that the c - met / hgf signaling pathway , as well as c - met overexpression , has a strong relationship with tumor cell proliferation , motility , invasion , tumor angiogenesis , and poor prognosis . a therapeutic agent targeting c - met and hgf is currently receiving attention .
meningiomas , as previously described , show high recurrence rates , even after curative resection of the tumors .
the recurrence rate depends on several prognostic factors , including the invasiveness of the tumor .
because invasive meningiomas show poor prognosis , the identification of their mechanism may be useful in the management of meningiomas .
several studies identify an association of c - met / hgf expression and clinical significance , and most of these studies imply an association between c - met / hgf expression and tumor recurrence in meningioma . in martinez - rumayor et al.s study , immunohistochemical co - expression of c - met / hgf
kim et al .   also shows that the expression of hgf and the co - expression of c - met / hgf are associated with the histologic grade of and recurrence of meningiomas by rtpcr .
in contrast , studies by karja et al .   and lamszus et al .  
use enzyme - linked immunosorbent assay and immunohistochemistry to argue that hgf is not related to tumor recurrence in meningioma   few studies demonstrate an association of c - met / hgf with brain and bone invasion of meningiomas .
the present study provides data on the expression of c - met and hgf in a large scale studies of meningiomas , as well as on the relationships of the meningiomas with brain and bone / soft tissue invasion in patients . in addition , the study shows that c - met is significantly associated with meningioma brain invasion , and that there is a tendency for increased c - met in meningiomas with bone / soft tissue invasion .
recent studies reveal that the c - met signaling cascade facilitates the invasion of cancer .
the downstream cascade signaling of activated c - met , by either autocrine or paracrine interaction , leads to the dissociation of tumor cells from the surrounding stromal tissue , resulting in tumor cell invasion .
our study supports these findings that c - met is closely related to tumor invasion .
one limitation of this study is that only a few cases of rare specific histologic subtypes are included in the data . nevertheless , the results suggest that c - met may participate in tumor invasion .
we also evaluate a possible association between the c - met and hgf expression and disease recurrence . in this study ,
the recurrence rate of meningiomas with complete tumor resection is 5% , a finding which is slightly lower than findings in previous reports . also , we demonstrate that c - met only shows a tendency for association with shorter rfs periods .
in general , the recurrence of meningiomas occurred within two years of surgical treatment , and up to 94% of patients with meningiomas experienced recurrence within five years .
however , the vast majority of meningiomas are slow - growing tumors , and benign meningiomas that have been completely removed from patients recur at a rate of 19% after 20 years of follow - up . thus our findings about recurrence rates are limited due to an insufficient follow - up period ( median follow - up time in this study , 26.7 months ) .
several studies report an intratumoral heterogeneity of c - met and hgf expression , revealing an increase in these factors at cancer - invading fronts in breast carcinoma and cholangiocarcinoma . accordingly
, further studies are needed to elucidate intratumoral heterogeneity in meningiomas , and the association between c - met overexpression and rfs . in summary ,
our results demonstrate that c - met is associated with the brain invasion of meningiomas , and that c - met expression may be useful predictive markers for meningioma recurrence .
many previous studies reveal that c - met signaling is involved in the progression and spread of several cancers [ 16 - 19,25,28 ] .
the collective understanding of c - met s role in cancers has evoked considerable interest in c - met and hgf as major targets in the development of cancer drugs .
this has led to the development of a variety of c - met pathway antagonists with potential clinical applications .
we conclude that c - met expression may be a useful predictive marker for meningioma recurrence , and that invasive meningiomas with high expression of c - met may be good candidates for targeted therapy using selective c - met inhibitors .
 background : meningiomas show high recurrence rates even after curative tumor removal . 
 the invasiveness of meningiomas may contribute to their high recurrence rates . 
 recently , c - met and hepatocyte growth factor ( hgf ) have been reported to be involved in cancer invasion.methods:we examined the immunohistochemical expression of c - met and hgf in 100 cases of patients with meningiomas who have undergone complete tumor removal.results:c-met-high and hgfhigh were found in 17% and 13% of meningiomas , respectively . 
 brain invasion was observed in 17.6% of c - met - high meningiomas , but in only 2.4% of c - met - low meningiomas ( p=.033 ) . 
 bone / soft tissue invasion was observed in 23.5% of c - met - high meningiomas and in 9.6% of c - met - low meningiomas ( p=.119 ) . 
 hgf - high did not show statistical association with brain invasion or bone / soft tissue invasion . 
 c - met - high demonstrated shorter recurrence - free survival ( rfs , 93.58.2 months vs 96.11.9 months ) ; however , this difference was not statistically significant ( p=.139 ) . 
 there was no association of hgf - high with rfs.conclusions:this study demonstrates that c- met - high is associated with brain invasion of meningiomas , and that c - met expression may be a useful predictive marker for meningioma recurrence . 
 patients with invasive meningiomas with high expressions of c - met may be good candidates for targeted therapy using c - met inhibitors . 