Abstract Background The aims of this study were to evaluate the incidence of synchronous appendiceal neoplasm in patients with colorectal cancer, and to determine its clinical significance. Methods Pathological reports and medical records were reviewed of patients with colorectal adenocarcinoma who underwent oncological resection of the tumor together with appendectomy at the Faculty of Medicine Siriraj Hospital, Mahidol University, Thailand between September 2000 and April 2008. Results This study included 293 patients with an average age of 62 years (range 19–95) and 51 percent were male. Of the patients studied, 228 (78 percent) had right hemicolectomy, whereas the others (22 percent) had surgery for left-sided colon cancer or rectal cancer. One patient (0.3 percent) had epithelial appendiceal neoplasm (mucinous cystadenoma) and 3 patients (1.0 percent) had metastatic colorectal cancer in the mesoappendix. However, the presence of synchronous appendiceal tumors and/or metastasis did not alter postoperative management, as these patients had received adjuvant therapy and were scheduled for surveillance program because of nodal involvement. Conclusion The incidence of synchronous primary appendiceal neoplasm and secondary (metastatic) appendiceal neoplasm in colorectal cancer patients was 0.3 and 1.0 percent, respectively. However, these findings did not change the postoperative clinical management.</p

A Sudirman

Akkrarash Vongjirad

BK Edwards

CY Lin

Darin Lohsiriwat

EB Goldstein

EM Murphy

H Mahteme

JB Albright

KL Hsu

L Filik

M Benedetti

M Pitiakoudis

M Wolff

ME O'Donnell

MH Lyda

MJ Solomon

ML McGory

MN Khan

OC Iwuagwu

PG Rose

S Varga

SS Nitecki

T Fujiwara

Varut Lohsiriwat

WV Melvin

English

PubMed

Springer - Publisher Connector

BioMed CentralWorld Journal of Surgical Oncology
ssOpen AcceResearch
Incidence of synchronous appendiceal neoplasm in patients with 
colorectal cancer and its clinical significance
Varut Lohsiriwat*, Akkrarash Vongjirad and Darin Lohsiriwat
Address: Department of Surgery, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand
Email: Varut Lohsiriwat* - bolloon@hotmail.com; Akkrarash Vongjirad - akkrarash@hotmail.com; Darin Lohsiriwat - sidls@mahidol.ac.th
* Corresponding author    
Abstract
Background: The aims of this study were to evaluate the incidence of synchronous appendiceal
neoplasm in patients with colorectal cancer, and to determine its clinical significance.
Methods: Pathological reports and medical records were reviewed of patients with colorectal
adenocarcinoma who underwent oncological resection of the tumor together with appendectomy
at the Faculty of Medicine Siriraj Hospital, Mahidol University, Thailand between September 2000
and April 2008.
Results: This study included 293 patients with an average age of 62 years (range 19–95) and 51
percent were male. Of the patients studied, 228 (78 percent) had right hemicolectomy, whereas
the others (22 percent) had surgery for left-sided colon cancer or rectal cancer. One patient (0.3
percent) had epithelial appendiceal neoplasm (mucinous cystadenoma) and 3 patients (1.0 percent)
had metastatic colorectal cancer in the mesoappendix. However, the presence of synchronous
appendiceal tumors and/or metastasis did not alter postoperative management, as these patients
had received adjuvant therapy and were scheduled for surveillance program because of nodal
involvement.
Conclusion: The incidence of synchronous primary appendiceal neoplasm and secondary
(metastatic) appendiceal neoplasm in colorectal cancer patients was 0.3 and 1.0 percent,
respectively. However, these findings did not change the postoperative clinical management.
Background
Synchronous colorectal cancer (CRC) has been reported
in 0.6–1.4 percent of patients and metachronous CRC in
1–8 percent of patients [1]. Any neoplastic change of the
colon and rectum could possibly affect the appendix
because the appendix is derived embryologically from the
large intestine and has a similar mucosal pattern to the
colon and rectum. The histological features of appendi-
ceal adenocarcinoma are also identical to those of color-
ectal adenocarcinoma [2]. Moreover, it has been reported
that almost a quarter of patients with appendiceal cancer
are found to have synchronous or metachronous neo-
plasms elsewhere in the large intestine [2,3].
Although there have been increasing advances in both
endoscopy and radiology, the appendiceal mucosa
remains inaccessible and the accuracy of preoperative
diagnosis of appendiceal neoplasm is still poor. During
an operation, a correct diagnosis is made in less than half
of the cases [4]. Several case reports of synchronous
Published: 2 June 2009
World Journal of Surgical Oncology 2009, 7:51 doi:10.1186/1477-7819-7-51
Received: 8 March 2009
Accepted: 2 June 2009
This article is available from: http://www.wjso.com/content/7/1/51
© 2009 Lohsiriwat et al; licensee BioMed Central Ltd. 
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), 
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Page 1 of 4
(page number not for citation purposes)
World Journal of Surgical Oncology 2009, 7:51 http://www.wjso.com/content/7/1/51appendiceal tumors in CRC patients have been published
in the literature [5-9], but only one study has explored its
incidence which is about 4 percent of CRC patients having
synchronous appendiceal neoplasm [7]. Given the diffi-
culty in diagnosis of appendiceal tumors and the certain
risk of synchronous and metachronous neoplasm of the
appendix, the question of whether an incidental appen-
dectomy should be performed in CRC patients has been
raised [5,7].
In attempt to address this question, it is first essential to
know the incidence and the biological significance of syn-
chronous appendiceal tumors in CRC patients. The aims
of this study were to evaluate the incidence of synchro-
nous appendiceal neoplasm in patients with resectable
CRC in a university hospital, and to determine the clinical
significance of these findings.
Methods
Pathological reports and medical records were retrospec-
tively reviewed of patients with colorectal adenocarci-
noma who underwent oncological resection of the tumor
together with appendectomy at the Department of Sur-
gery, Faculty of Medicine Siriraj Hospital, Mahidol Uni-
versity, Bangkok, Thailand between September 2000 and
April 2008. Patients were excluded if they had familial
adenomatous polyposis syndrome or had had a previous
appendectomy, or if there had been direct invasion of
CRC to the appendix. Patients receiving neoadjuvant ther-
apy were also excluded. Notably, there were about 100–
120 operations for CRC per annum in our unit, and one-
third of them were for right-sided colon cancer.
The appendix is normally a part of the specimen removed
in patients with right hemicolectomy. All the appendices
removed along with the right colon specimen were sys-
tematically analyzed. Incidental appendectomy had also
been performed in patients who had undergone left hemi-
colectomy or rectal resection at the discretion of the sur-
geon. We tended to perform incidental appendectomy if
the patient was younger than 45 years, or there was a fec-
alith in the appendix. Histopathological study of the
appendix included gross and microscopic examination.
Specimens were sectioned at the tip, body, and base of the
appendix as well as other suspicious lesions. All speci-
mens were examined by a consultant or senior patholo-
gist.
The site of the primary tumor, type of operation, and
pathological staging of CRC were noted. Macroscopic and
microscopic features of the appendix were also recorded.
The presence of synchronous appendiceal tumors and/or
metastasis was correlated with follow-up data to demon-
strate the clinical significance of these findings. The study
was approved by the Institutional Ethics Committee.
Results
Two hundred and ninety-three patients were included in
this study. The patients studied had an average age of 62
years (range 19–95) and 51 percent were male. Of the
patients studied, 228 (78 percent) had a right hemicolec-
tomy, 45 (15 percent) had a left hemicolectomy, and 20
(7 percent) had surgery for rectal cancer. One patient (0.3
percent) had epithelial appendiceal neoplasm (mucinous
cystadenoma), and 3 patients (1.0 percent) had metastatic
colorectal cancer in the mesoappendix (Table 1). All met-
astatic lesions were mucinous adenocarcinoma. Clusters
of metastatic cancerous cells were 1–5 mm in diameter;
primarily located in the subserosal area. All appendices
with neoplasms did not appear abnormal in the preoper-
ative imaging and during the intraoperative examination.
However, the case of metastases in the mesoappendix
from a descending colon cancer was associated to other
peritoneal implants.
There was no specific morbidity that could be attributed
to incidental appendectomy in the present study. The
presence of synchronous appendiceal tumors and/or
metastasis did not alter postoperative management, as
these patients had received adjuvant therapy and were
scheduled for surveillance program because of nodal
involvement.
Discussion
The question of whether an incidental appendectomy
should be performed in CRC patients has been raised due
to the difficulty in diagnosis of appendiceal tumors and
the certain risk of synchronous and metachronous neo-
plasm of the appendix [5,7]. Little is known about the
incidence of appendiceal neoplasm in CRC patients. To
Table 1: Patients' characteristics, details of primary colorectal cancer, and pathological results of synchronous appendiceal neoplasm
Age (years)/Gender Primary tumor Type of surgery Staging of primary tumor Appendix abnormality
59 M cecum RH T3N2 Metastatic adenocarcinoma in the mesoappendix
62 F ascending colon RH T3N2 metastatic adenocarcinoma in the mesoappendix
48 M descending colon LH T3N1 Metastatic adenocarcinoma in the mesoappendix
64 F rectum APR T3N2 mucinous cystadenoma
Abbreviation: RH (right hemicolectomy), LH (left hemicolectomy), APR (abdominoperineal resection)Page 2 of 4
(page number not for citation purposes)
World Journal of Surgical Oncology 2009, 7:51 http://www.wjso.com/content/7/1/51the best of our knowledge, there was only one study deter-
mining such an incidence [7]. Khan and Moran retrospec-
tively reviewed 169 CRC patients who underwent CRC
surgery and removal of the appendix in Basingstoke,
United Kingdom. They reported 4.1 percent synchronous
primary appendiceal neoplasm in these patients, and
mucinous cystadenoma was the most common neoplasm
found [7]. Furthermore, these authors suggested perform-
ing incidental appendectomy in all CRC patients. Mean-
while, Albright et al determined the cost-effectiveness of
interval appendectomy in patients who undergo curative
resection for CRC and found that the benefit in cost was
only realized for patients younger than 45 years of age [5].
Synchronous CRC and appendiceal tumors have been
observed in high-risk patients such as those with long-
standing ulcerative colitis [10]. Moreover, patients with
rectal cancer had a slightly higher rate of synchronous
appendiceal tumors than those with right-sided colon
cancer [7]. However, absent from the literature are such
studies in Asian population, in which the incidence of
synchronous appendiceal neoplasms in CRC patients
could be different.
The present study in Thailand demonstrates that the inci-
dence of synchronous primary appendiceal neoplasm and
secondary (metastatic) appendiceal neoplasm in patients
with resectable CRC is 0.3 and 1.0 percent, respectively.
One possible explanation for the low incidence of syn-
chronous primary neoplasm of the appendix in CRC
patients in the present study could be that tumorigenesis
of the appendix and other parts of the large intestine are
not the same. Appendiceal mucosa is not directly exposed
to potential carcinogens in fecal material as the colorectal
mucosa is. Epidemiological study revealed that appendi-
ceal tumors account for 0.4–1 percent of alimentary tract
cancers and are found in 0.7–1.7 percent of appendec-
tomy specimens [11], whilst CRC is the most common
gastrointestinal malignancy [12]. Also, the peak incidence
of appendiceal neoplasm is in patients in their early for-
ties, 20-year younger than that of CRC [13]. It is possible
that the incidence of appendiceal tumors in Asian popu-
lation is different from that of Western population [14],
and thus the incidence of synchronous appendieal neo-
plasms in CRC patients could vary among various ethnic
and geographic backgrounds. Lastly, in view of the exam-
ination of the specimens, different protocols of tissue sec-
tion and methods of histopathological examination may
lead to differences in the incidence percentages.
The unexpected finding in the present study was that one
percent of CRC patients had metastatic lesions in the mes-
oappendix. This finding was fairly consistent with a previ-
ous study by Albright and his colleagues [5]. They
reported 2 cases of metastatic implants to the appendix
from routine interval appendectomy in 210 patients with
intraabdominal malignancy; accounting for 0.95%. One
case was secondary to a sigmoid cancer with limited peri-
toneal carcinomatosis while the other was secondary to an
ovarian adenocarcinoma. As the mesoappendix encloses
the appendiceal artery and vein, together with lymphatic
vessels and lymph node, metastasis to the mesoappendix
could occur via the lymphatic, hematogenous or transcoe-
lomic route. With regard to the transcoelomic route, CRC
may spread throughout the peritoneum either via the sub-
peritoneal lymphatic drainage or by viable cells being
shed from the serosal surface of a tumor [15]. This is sup-
ported by the observations that 14.6 percent of CRC had
positive cytology for cancer cells on the peritoneal or per-
irectal surface of the bowel, particularly in those with
extensive lymphatic involvement, poorly differentiated
tumors, or liver metastases [16]. Metastasis to the appen-
dix has been reported in both gastrointestinal and non-
gastrointestinal malignancies such as gastric [17], pancre-
atic [18], ovarian [5,19], cervical [20], nasopharyngeal
[21], breast [22], and lung [23].
A limitation of this single-center study is a relatively small
sample size, particularly those with left-sided colon cancer
and rectal cancer. Considering this reason, a larger
number of incidental appendectomy in patients with left-
sided colon cancer and rectal cancer are warranted to ver-
ify our findings. Besides, this review has some limitations
which are mainly inherent to a retrospective study and to
different clinical judgments of surgeons. There could be a
selection bias to perform incidental appendectomy as we
did not have specific criteria for performing appendec-
tomy in CRC patient at our institute. It is possible that the
appendix was more likely to be removed because of its
abnormal appearance. In order to determine the true inci-
dence of synchronous appendiceal neoplasms, a cohort or
prospective study of patients where the appendix is always
removed (either by necessity in a right hemicolectomy
specimen; or as a protocol where the appendix is always
removed in CRC patients) is required.
Conclusion
Based on this study, the incidence of synchronous pri-
mary appendiceal neoplasm and secondary (metastatic)
appendiceal neoplasm in CRC patients was 0.3 and 1.0
percent, respectively. These findings did not change the
postoperative clinical management.
Abbreviations
APR: abdominoperineal resection; CRC: colorectal cancer;
LH: left hemicolectomy; RH: right hemicolectomy.
Competing interests
The authors declare that they have no competing interests.Page 3 of 4
(page number not for citation purposes)
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Authors' contributions
VL was the principal investigator who participated in
research design, analyzed the data, and prepared the man-
uscript. AV contributed to acquisition and analysis of
data. DL conceived of the study, participated in its design
and coordination, and helped to draft the manuscript. All
authors read and approved the final manuscript.
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Incidence of synchronous appendiceal neoplasm in patients with colorectal cancer and its clinical significance

Crossref

Abstract Background The aims of this study were to evaluate the incidence of synchronous appendiceal neoplasm in patients with colorectal cancer, and to determine its clinical significance. Methods Pathological reports and medical records were reviewed of patients with colorectal adenocarcinoma who underwent oncological resection of the tumor together with appendectomy at the Faculty of Medicine Siriraj Hospital, Mahidol University, Thailand between September 2000 and April 2008. Results This study included 293 patients with an average age of 62 years (range 19–95) and 51 percent were male. Of the patients studied, 228 (78 percent) had right hemicolectomy, whereas the others (22 percent) had surgery for left-sided colon cancer or rectal cancer. One patient (0.3 percent) had epithelial appendiceal neoplasm (mucinous cystadenoma) and 3 patients (1.0 percent) had metastatic colorectal cancer in the mesoappendix. However, the presence of synchronous appendiceal tumors and/or metastasis did not alter postoperative management, as these patients had received adjuvant therapy and were scheduled for surveillance program because of nodal involvement. Conclusion The incidence of synchronous primary appendiceal neoplasm and secondary (metastatic) appendiceal neoplasm in colorectal cancer patients was 0.3 and 1.0 percent, respectively. However, these findings did not change the postoperative clinical management.</p

Lohsiriwat Darin

Vongjirad Akkrarash

Lohsiriwat Varut

Directory of Open Access Journals

BioMed  CentralPage 1 of 4(page number not for citation purposes)World Journal of Surgical OncologyOpen Access ResearchIncidence of synchronous appendiceal neoplasm in patients with colorectal cancer and its clinical significanceVarut Lohsiriwat*, Akkrarash Vongjirad and Darin LohsiriwatAddress: Department of Surgery, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, ThailandEmail: Varut Lohsiriwat* - bolloon@hotmail.com; Akkrarash Vongjirad - akkrarash@hotmail.com; Darin Lohsiriwat - sidls@mahidol.ac.th* Corresponding author    AbstractBackground: The aims of this study were to evaluate the incidence of synchronous appendicealneoplasm in patients with colorectal cancer, and to determine its clinical significance.Methods: Pathological reports and medical records were reviewed of patients with colorectaladenocarcinoma who underwent oncological resection of the tumor together with appendectomyat the Faculty of Medicine Siriraj Hospital, Mahidol University, Thailand between September 2000and April 2008.Results: This study included 293 patients with an average age of 62 years (range 19–95) and 51percent were male. Of the patients studied, 228 (78 percent) had right hemicolectomy, whereasthe others (22 percent) had surgery for left-sided colon cancer or rectal cancer. One patient (0.3percent) had epithelial appendiceal neoplasm (mucinous cystadenoma) and 3 patients (1.0 percent)had metastatic colorectal cancer in the mesoappendix. However, the presence of synchronousappendiceal tumors and/or metastasis did not alter postoperative management, as these patientshad received adjuvant therapy and were scheduled for surveillance program because of nodalinvolvement.Conclusion:  The incidence of synchronous primary appendiceal neoplasm and secondary(metastatic) appendiceal neoplasm in colorectal cancer patients was 0.3 and 1.0 percent,respectively. However, these findings did not change the postoperative clinical management.BackgroundSynchronous colorectal cancer (CRC) has been reportedin 0.6–1.4 percent of patients and metachronous CRC in1–8 percent of patients [1]. Any neoplastic change of thecolon and rectum could possibly affect the appendixbecause the appendix is derived embryologically from thelarge intestine and has a similar mucosal pattern to thecolon and rectum. The histological features of appendi-ceal adenocarcinoma are also identical to those of color-ectal adenocarcinoma [2]. Moreover, it has been reportedthat almost a quarter of patients with appendiceal cancerare found to have synchronous or metachronous neo-plasms elsewhere in the large intestine [2,3].Although there have been increasing advances in bothendoscopy and radiology, the appendiceal mucosaremains inaccessible and the accuracy of preoperativediagnosis of appendiceal neoplasm is still poor. Duringan operation, a correct diagnosis is made in less than halfof the cases [4]. Several case reports of synchronousPublished: 2 June 2009World Journal of Surgical Oncology 2009, 7:51 doi:10.1186/1477-7819-7-51Received: 8 March 2009Accepted: 2 June 2009This article is available from: http://www.wjso.com/content/7/1/51© 2009 Lohsiriwat et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.World Journal of Surgical Oncology 2009, 7:51 http://www.wjso.com/content/7/1/51Page 2 of 4(page number not for citation purposes)appendiceal tumors in CRC patients have been publishedin the literature [5-9], but only one study has explored itsincidence which is about 4 percent of CRC patients havingsynchronous appendiceal neoplasm [7]. Given the diffi-culty in diagnosis of appendiceal tumors and the certainrisk of synchronous and metachronous neoplasm of theappendix, the question of whether an incidental appen-dectomy should be performed in CRC patients has beenraised [5,7].In attempt to address this question, it is first essential toknow the incidence and the biological significance of syn-chronous appendiceal tumors in CRC patients. The aimsof this study were to evaluate the incidence of synchro-nous appendiceal neoplasm in patients with resectableCRC in a university hospital, and to determine the clinicalsignificance of these findings.MethodsPathological reports and medical records were retrospec-tively reviewed of patients with colorectal adenocarci-noma who underwent oncological resection of the tumortogether with appendectomy at the Department of Sur-gery, Faculty of Medicine Siriraj Hospital, Mahidol Uni-versity, Bangkok, Thailand between September 2000 andApril 2008. Patients were excluded if they had familialadenomatous polyposis syndrome or had had a previousappendectomy, or if there had been direct invasion ofCRC to the appendix. Patients receiving neoadjuvant ther-apy were also excluded. Notably, there were about 100–120 operations for CRC per annum in our unit, and one-third of them were for right-sided colon cancer.The appendix is normally a part of the specimen removedin patients with right hemicolectomy. All the appendicesremoved along with the right colon specimen were sys-tematically analyzed. Incidental appendectomy had alsobeen performed in patients who had undergone left hemi-colectomy or rectal resection at the discretion of the sur-geon. We tended to perform incidental appendectomy ifthe patient was younger than 45 years, or there was a fec-alith in the appendix. Histopathological study of theappendix included gross and microscopic examination.Specimens were sectioned at the tip, body, and base of theappendix as well as other suspicious lesions. All speci-mens were examined by a consultant or senior patholo-gist.The site of the primary tumor, type of operation, andpathological staging of CRC were noted. Macroscopic andmicroscopic features of the appendix were also recorded.The presence of synchronous appendiceal tumors and/ormetastasis was correlated with follow-up data to demon-strate the clinical significance of these findings. The studywas approved by the Institutional Ethics Committee.ResultsTwo hundred and ninety-three patients were included inthis study. The patients studied had an average age of 62years (range 19–95) and 51 percent were male. Of thepatients studied, 228 (78 percent) had a right hemicolec-tomy, 45 (15 percent) had a left hemicolectomy, and 20(7 percent) had surgery for rectal cancer. One patient (0.3percent) had epithelial appendiceal neoplasm (mucinouscystadenoma), and 3 patients (1.0 percent) had metastaticcolorectal cancer in the mesoappendix (Table 1). All met-astatic lesions were mucinous adenocarcinoma. Clustersof metastatic cancerous cells were 1–5 mm in diameter;primarily located in the subserosal area. All appendiceswith neoplasms did not appear abnormal in the preoper-ative imaging and during the intraoperative examination.However, the case of metastases in the mesoappendixfrom a descending colon cancer was associated to otherperitoneal implants.There was no specific morbidity that could be attributedto incidental appendectomy in the present study. Thepresence of synchronous appendiceal tumors and/ormetastasis did not alter postoperative management, asthese patients had received adjuvant therapy and werescheduled for surveillance program because of nodalinvolvement.DiscussionThe question of whether an incidental appendectomyshould be performed in CRC patients has been raised dueto the difficulty in diagnosis of appendiceal tumors andthe certain risk of synchronous and metachronous neo-plasm of the appendix [5,7]. Little is known about theincidence of appendiceal neoplasm in CRC patients. ToTable 1: Patients' characteristics, details of primary colorectal cancer, and pathological results of synchronous appendiceal neoplasmAge (years)/Gender Primary tumor Type of surgery Staging of primary tumor Appendix abnormality59 M cecum RH T3N2 Metastatic adenocarcinoma in the mesoappendix62 F ascending colon RH T3N2 metastatic adenocarcinoma in the mesoappendix48 M descending colon LH T3N1 Metastatic adenocarcinoma in the mesoappendix64 F rectum APR T3N2 mucinous cystadenomaAbbreviation: RH (right hemicolectomy), LH (left hemicolectomy), APR (abdominoperineal resection)World Journal of Surgical Oncology 2009, 7:51 http://www.wjso.com/content/7/1/51Page 3 of 4(page number not for citation purposes)the best of our knowledge, there was only one study deter-mining such an incidence [7]. Khan and Moran retrospec-tively reviewed 169 CRC patients who underwent CRCsurgery and removal of the appendix in Basingstoke,United Kingdom. They reported 4.1 percent synchronousprimary appendiceal neoplasm in these patients, andmucinous cystadenoma was the most common neoplasmfound [7]. Furthermore, these authors suggested perform-ing incidental appendectomy in all CRC patients. Mean-while, Albright et al determined the cost-effectiveness ofinterval appendectomy in patients who undergo curativeresection for CRC and found that the benefit in cost wasonly realized for patients younger than 45 years of age [5].Synchronous CRC and appendiceal tumors have beenobserved in high-risk patients such as those with long-standing ulcerative colitis [10]. Moreover, patients withrectal cancer had a slightly higher rate of synchronousappendiceal tumors than those with right-sided coloncancer [7]. However, absent from the literature are suchstudies in Asian population, in which the incidence ofsynchronous appendiceal neoplasms in CRC patientscould be different.The present study in Thailand demonstrates that the inci-dence of synchronous primary appendiceal neoplasm andsecondary (metastatic) appendiceal neoplasm in patientswith resectable CRC is 0.3 and 1.0 percent, respectively.One possible explanation for the low incidence of syn-chronous primary neoplasm of the appendix in CRCpatients in the present study could be that tumorigenesisof the appendix and other parts of the large intestine arenot the same. Appendiceal mucosa is not directly exposedto potential carcinogens in fecal material as the colorectalmucosa is. Epidemiological study revealed that appendi-ceal tumors account for 0.4–1 percent of alimentary tractcancers and are found in 0.7–1.7 percent of appendec-tomy specimens [11], whilst CRC is the most commongastrointestinal malignancy [12]. Also, the peak incidenceof appendiceal neoplasm is in patients in their early for-ties, 20-year younger than that of CRC [13]. It is possiblethat the incidence of appendiceal tumors in Asian popu-lation is different from that of Western population [14],and thus the incidence of synchronous appendieal neo-plasms in CRC patients could vary among various ethnicand geographic backgrounds. Lastly, in view of the exam-ination of the specimens, different protocols of tissue sec-tion and methods of histopathological examination maylead to differences in the incidence percentages.The unexpected finding in the present study was that onepercent of CRC patients had metastatic lesions in the mes-oappendix. This finding was fairly consistent with a previ-ous study by Albright and his colleagues [5]. Theyreported 2 cases of metastatic implants to the appendixfrom routine interval appendectomy in 210 patients withintraabdominal malignancy; accounting for 0.95%. Onecase was secondary to a sigmoid cancer with limited peri-toneal carcinomatosis while the other was secondary to anovarian adenocarcinoma. As the mesoappendix enclosesthe appendiceal artery and vein, together with lymphaticvessels and lymph node, metastasis to the mesoappendixcould occur via the lymphatic, hematogenous or transcoe-lomic route. With regard to the transcoelomic route, CRCmay spread throughout the peritoneum either via the sub-peritoneal lymphatic drainage or by viable cells beingshed from the serosal surface of a tumor [15]. This is sup-ported by the observations that 14.6 percent of CRC hadpositive cytology for cancer cells on the peritoneal or per-irectal surface of the bowel, particularly in those withextensive lymphatic involvement, poorly differentiatedtumors, or liver metastases [16]. Metastasis to the appen-dix has been reported in both gastrointestinal and non-gastrointestinal malignancies such as gastric [17], pancre-atic [18], ovarian [5,19], cervical [20], nasopharyngeal[21], breast [22], and lung [23].A limitation of this single-center study is a relatively smallsample size, particularly those with left-sided colon cancerand rectal cancer. Considering this reason, a largernumber of incidental appendectomy in patients with left-sided colon cancer and rectal cancer are warranted to ver-ify our findings. Besides, this review has some limitationswhich are mainly inherent to a retrospective study and todifferent clinical judgments of surgeons. There could be aselection bias to perform incidental appendectomy as wedid not have specific criteria for performing appendec-tomy in CRC patient at our institute. It is possible that theappendix was more likely to be removed because of itsabnormal appearance. In order to determine the true inci-dence of synchronous appendiceal neoplasms, a cohort orprospective study of patients where the appendix is alwaysremoved (either by necessity in a right hemicolectomyspecimen; or as a protocol where the appendix is alwaysremoved in CRC patients) is required.ConclusionBased on this study, the incidence of synchronous pri-mary appendiceal neoplasm and secondary (metastatic)appendiceal neoplasm in CRC patients was 0.3 and 1.0percent, respectively. These findings did not change thepostoperative clinical management.AbbreviationsAPR: abdominoperineal resection; CRC: colorectal cancer;LH: left hemicolectomy; RH: right hemicolectomy.Competing interestsThe authors declare that they have no competing interests.Publish with BioMed Central    and   every scientist can read your work free of charge"BioMed Central will be the most significant development for disseminating the results of biomedical research in our lifetime."Sir Paul Nurse, Cancer Research UKYour research papers will be:available free of charge to the entire biomedical communitypeer reviewed and published  immediately upon acceptancecited in PubMed and archived on PubMed Central yours — you keep the copyrightSubmit your manuscript here:http://www.biomedcentral.com/info/publishing_adv.aspBioMedcentralWorld Journal of Surgical Oncology 2009, 7:51 http://www.wjso.com/content/7/1/51Page 4 of 4(page number not for citation purposes)Authors' contributionsVL was the principal investigator who participated inresearch design, analyzed the data, and prepared the man-uscript. AV contributed to acquisition and analysis ofdata. DL conceived of the study, participated in its designand coordination, and helped to draft the manuscript. Allauthors read and approved the final manuscript.References1. Benedetti M, Tinozzi FP, Dini S, Albertario S, Rossi G, Bianchi C,Tinozzi S: Synchronous and metachronous tumours of coloncancer. A review of 5 years of experience (1999–2004).  AnnItal Chir 2006, 77:233-239.2. Wolff M, Ahmed N: Epithelial neoplasms of the vermiformappendix (exclusive of carcinoid). II. Cystadenomas, papil-lary adenomas, and adenomatous polyps of the appendix.Cancer 1976, 37:2511-2522.3. Iwuagwu OC, Jameel JK, Drew PJ, Hartley JE, Monson JR: Primarycarcinoma of the appendix – Hull series.  Dig Surg 2005,22:163-167.4. Nitecki SS, Wolff BG, Schlinkert R, Sarr MG: The natural historyof surgically treated primary adenocarcinoma of the appen-dix.  Ann Surg 1994, 219:51-57.5. 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Incidence of synchronous appendiceal neoplasm in patients with colorectal cancer and its clinical significance

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