Open Journal of Gastroenterology, 2013, 3, 267-271 OJGas
http://dx.doi.org/10.4236/ojgas.2013.35045 Published Online September 2013 (http://www.scirp.org/journal/ojgas/)
Primary Extra-Gastrointestinal Stromal Tumor (GIST)
arising from mesentery of small bowel and presenting as
abdominal mass: A rare entity
Alok Kumar Tiwari1*, Anil Kumar Choudhary2, Hemant Khowal1, Poras Chaudhary1,
Mohinder P. Arora1
1Department of Surgery, Lady Hardinge Medical College, New Delhi, India
2Department of Surgery, Dr R.M.L Hospital, New Delhi, India
Received 20 July 2013; revised 21 August 2013; accepted 29 August 2013
Copyright © 2013 Alok Kumar Tiwari et al. This is an open access article distributed under the Creative Commons Attribution Li-
cense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
ABSTRACT
Introduction: Majority of mesenchymal tumors of
gastrointestinal tract are Gastrointestinal Stromal
Tumor (GIST). It is, however, a rare tumor, account-
ing for less than 1% of primary gastrointestinal (GI)
neoplasms. Though, these tumors are refractory to
conventional chemotherapy or radiotherapy but show
a good response to targeted adjuvant chemotherapy
with tyrosine kinase inhibitors following surgical re-
section. Case Report: we report here a case of pri-
mary Extra-GIST tumor arising from mesentry of
small bowel near duodeno-jejunal junction in a 69
years old male patient. The patient presented with a
palpable mass in upper abdomen for past 15 days. On
examination, a non-tender mobile lump of size around
17 × 10 cm, with bosselated surface and firm in con-
sistency was palpable involving epigastric, left hypo-
chondrium and umbilical region. Contrast enhanced
computed tomography of abdomen revealed a het-
erogenous mesentric mass. On surgical intervention a
mass was found involving mesentery near dudeno-
jejunal junction without involvement of gastrointes-
tinal tract. Complete surgical resection of the tumor
was done and adjuvant chemotherapy with Imatinib
mesylate was started as HPE revealing GIST with
mitotic index of >10/50 HPF and 17 × 10 cm size
placed the patient in high risk category. Patient was
discharged on 12th of post-operative day with advice
of regular follow-up. Conclusion: GIST occurrence is
not restricted to bowel but can involve unusual sites
also. The mainstay of treatment remains surgical re-
section with adequate margin. In cases where tumour
has malignant potential (high mitotic figures on histo-
pathology) adjuvent treatment with tyrosine kinase
may prevent or delay relapse.
Keywords: Extra-Gastrointestinal Stromal Tumors;
GIST; Mesentric Tumors; Imatinib Mesylate; Abdominal
Mass
1. INTRODUCTION
Gastrointestinal Stromal Tumors coined by Mazur and
Clark are the most common mesenchymal tumors of gas-
trointestinal tract found to be immunohistochemically
and ultrastructurally different from other spindle cell
tumors [1]. GISTs can occur anywhere in the gastrointes-
tinal (GI) tract, commonest site being stomach (Ap-
proximately 60% - 70% of GISTs), followed by small
intestine (25% - 35%), colon, rectum, appendix (together
5%), and esophagus (2% - 3%). Rarely, they may arise
from the mesentery or omentum [2].
The clinical manifestations of GISTs depend on the
location and size of the tumors and are often nonspecific
although patients with advanced disease may present
with symptoms of a mass lesion, abdominal pain, or
bleeding [3,4].
The availability of the KIT tyrosine kinase inhibitor
(STI-571, imatinib/Gleevec/Novartis) has revolutionized
the treatment of gastrointestinal stromal tumors, thereby
making it important to know this disease entity.
We report here a case of extra-gastrointestinal stromal
tumor arising from mesentery of small intestine present-
ing as an abdominal mass.
2. CASE REPORT
A 69 years old male patient presented with history of
*Corresponding author.

A. K. Tiwari et al. / Open Journal of Gastroenterology 3 (2013) 267-271 268
progressively increasing mass in upper abdomen without
any other significant complaints for last 15 days. When
evaluated clinically patient was found haemodynamically
stable and his per-abdominal examination revealed a
mass of size 17 × 10 cm which was mobile , non-tender,
with bosselated surface and firm in consistency involving
epigastric , left hypochondrium and umbilical region.
His laboratory workups were unremarkable and Con-
trast Enhanced Computed Tomography (CECT) of ab-
domen depicted a heterogenous mesentric mass (Figure
1).
On laparotomy, 17 × 10 cm mass involving the mes-
entery (Figure 2) near the duodeno-jejunal junction was
found without any gross evidence of gastrointestinal tract
involvement, peritoneal deposits, ascitis and lymph node
enlargement. Resection of the tumor along with the
mesentery and ligation of the feeding vessels was carried
out and specimen was sent for histopathological exami-
nation.
Figure 1. CECT abdomen showing a heterogenous mass (ar-
row).
Figure 2. Large mesenteric mass near duodeno-jejunal junction
(thin arrow) away from transverse colon (thick short arrow) and
small intestine (thick long arrow).
Histopathological examination grossly revealed grey
white soft tissue mass of size 17 × 10 cm with encapsu-
lated and nodular external surface. Microscopical ex-
amination showed features of malignant spindle cell tu-
mors arranged in short fascicles and focally forming
whorls with myxoid areas and multiple foci of necrosis.
Individual tumor cells revealed moderate nuclear pleo-
morphism, brisk mitosis (>10/HPF). On the basis of im-
munohistochemistry, the tumor cells were found to be
positive for Vimentin/smooth muscle actin/(SMA) and
CD-117.
The patient was discharged on 12th of post operative
day on Imatinib mesylate adjuvent chemotherapy and is
on regular follow up.
3. DISCUSSION
Gastro-Intestinal Stromal Tumor (GIST) appears to arise
from the interstitial cell of Cajal [5,6] but the exact cell
of origin and precise steps in tumorogenesis are not well
established. However, mutation in the proto-oncogene
c-kit leading to increased expression of KIT (type III
tyrosine kinase receptor) and platelet-derived growth fac-
tor receptor-alpha (PDGFRA, found in 5% - 10%) and
loss of heterozygosity of the NF1 gene are thought to
play a major role.
Microscopically GISTs are classified into: spindle cell
type (70%), epitheloid type (20%), and mixed spindle
cell and epithelioid cell type. On immunohistochemical
staining, 95% are CD117 (c-kit) positive, 70% are CD34,
and 40% stain positive for smooth muscle actin.
Liver and peritoneum are the most common sites of
metastasis via hematogenous route while metastasis to
the lung, bones, and lymph nodes is rare.
GISTs may grow into large size by displacing adjacent
structures rather than invading them and so they are
symptomatic where as small tumors are asymptomatic.
The symptoms expressed are non-specific GI symptoms
such as nausea, vomiting, dyspepsia, abdominal pain,
distension, or change in bowel behavior. The symptoms
of obstruction, bleeding, or rupture into the peritoneal
cavity are less common.
GISTs initially presenting as an abdominal mass are
exceedingly rare, and only 21 such cases including 4
cases involving only mesentery as primary site have been
reported in the world literature since 2001 [7-10].
In accordance with all larger clinicopathologic series,
GISTs have a predilection to adults over 50 years of age
with the median ages varying between 55 - 65 years in
different sites with no clear sex predilection. Whereas the
proportion of patients under 40 years of age ranged be-
tween 5% and 20% but they are reported to be extremely
rare in children.
A number of GISTs have been reported outside the

A. K. Tiwari et al. / Open Journal of Gastroenterology 3 (2013) 267-271 269
Gastrointestinal (GI) tract in the abdomen as a result of
metastasis from GI-tract proper specifically in omentum,
mesenteries, retroperitoneum and urinary bladder serosa
[11,12]. However, GIST originating from these sites as a
primary tumor is rare. The primary site of disseminated
intra-abdominal GIST involving multiple intestines, peri-
toneal surfaces and other abdominal organ is often im-
possible to ascertain. More commonly, GISTs in these lo-
cations represents intra-abdominal metastases from gas-
tric or intestinal primaries. Search of origin of primary
tumor whether it is from stomach or intestines is always
necessary for apparent extra-GI GISTs.
Small GISTs are often firm and sometimes rubbery,
whereas larger and malignant GISTs tend to be soft with
fish-flesh or lymphoma-like consistency.
In order to carry out detection, staging, surgical plan-
ning and follow-up of patients with GIST, CT, MRI and
fluorine-18-fluorodeoxyglucose (FDG) positron emission
tomography (PET) are considered to be the imaging mo-
dality of choice. The majority of GISTs appear to be well-
defined, extraluminal or intramural masses with varying
attenuation on CT. Small lesions, which are usually be-
nign, tend to be well-defined and relatively homogene-
ous, While larger lesions normally show well-defined or
ill-defined margins, inhomogeneous density both on un-
enhanced and on contrast-enhanced scans and a tendency
to spread to surrounding structures. Large tumors (>6 cm)
frequently show central areas of necrosis or haemorrhage
[13].
Primary gastrointestinal stromal tumor in the omentum
and mesentery can be suggested as a diagnosis in a pa-
tient with a well-marginated, lobulated mass that con-
tains large areas of low attenuation and lacks central gas.
The imaging appearance of mesenteric and omental GISTs
is indistinguishable from that of other sarcomas that may
arise in these locations [11].
Unlike gastrointestinal adenocarcinomas, GISTs me-
tastasizing to the lymph nodes are extremely rare. The
CT characteristics of metastatic lesions of GISTs are si-
milar to those of primary tumors, enhancing masses that
can be heterogeneous because of necrosis, hemorrhage,
or cystic degeneration.
4. TREATMENT
The treatment goal for localized primary GIST is com-
plete resection followed by adjuvant chemotherapy with-
out the need for lymphadenectomy or wide resection
margins.
Neoadjuvant Imatinib is not recommended where a
change in tumor size will not affect surgery [14]. It can,
however, be considered where a tumor response could
permit function-sparing surgery, e.g., rectum or oesopha-
gus.
The tumor should be removed en bloc with a clear
margin. The pseudocapsule should be removed and not
be penetrated. Therefore, either a wedge resection in case
of stomach or segmental resection in case of intestine is
required.
Lymph node dissection or biopsy is not recommended
mainly due to the pattern of spread of GISTs because
lymph node metastases are rare.
GIST shows a very dramatic response to a Tyrosine
kinase inhibitor, Imatinib mesylate (STI-571/Gleevec/
Novartis/Basel). This drug is a molecular targeted ther-
apy, and acts on the c-kit growth factor receptor, which is
the most important diagnostic marker of GISTs. This
drug also inhibits several other tyrosine kinase receptors
with varying affinity as also the BCR-ABL fusion pro-
tein and the platelet derived growth factor receptor
(PDGFR). The cases resistant to Imatinib or showing pro-
gression can be controlled by sunitinib malate (SU11248/
Sutent).
In general practice, contrast-enhanced CT is routinely
used to monitor tumor response following treatment with
tyrosine kinase inhibitors. The degree and pattern of en-
hancement observed on CT scans are useful for identify-
ing post treatment changes. On Contrast-Enhanced Com-
puted Tomography (CECT), a response to Imatinib is
characterized by rapid transition from a heterogeneously
hyper-attenuating pattern to a homogeneously hypo-at-
tenuating pattern with resolution of the enhanced tumor
nodules and a decrease in tumor vessels.
The density of hepatic metastases decreases after treat-
ment to approximately 20 - 25 H, which is near to, but
greater than that for a true cyst (<15 H). Follow-up CT
scans showing that the mass has become homogeneous
with significant decreases in the attenuation and size of
the tumor indicate a good response to imatinib [13].
Tumor size, anatomic location, and mitotic count are
considered independent prognostic factors for GISTs
[15,16] and tumors that measure ≥5 cm in size are asso-
ciated with an unfavorable prognosis. The anatomic site
of origin of a GIST is associated strongly with its clinical
behavior. The patients who have tumors arising in the
rectum or small intestine have the worst prognosis as
compared to the patients who have esophageal and gas-
tric neoplasms [16]. Likewise, GISTs that exhibit ≥5
mitoses per 50 HPF or ≥2 mitotic figures per 10 HPF are
associated with an unfavorable prognosis regardless of
their site of origin [15,17].
In a series of 200 GISTs, median survival was 66
months for complete resection compared with 22 months
for incomplete resection or unresectable disease [18].
Spontaneous tumor rupture, or rupture during surgery,
increases the risk of peritoneal recurrence and is an ad-
verse prognostic factor. Overall 5-year survival rates for
primary resected disease are in the order of 50% - 55%.

A. K. Tiwari et al. / Open Journal of Gastroenterology 3 (2013) 267-271 270
Most recurrences occurs within the first 2 years of re-
section necessitating the regular follow up of these pa-
tients.
A high risk patient should have a CT scan every 3 - 4
months for 3 years, then every 6 months to 5 years. For
low risk, a CT scan every 6 months for 5 years is ac-
ceptable [14].
GISTs of the jejunum and ileum treated surgically
have been shown to have a 39% tumor related mortality,
which was twice that of gastric GISTs [19].
Our case had mesenteric stromal tumor near duodeno-
jejunal junction, mitoses were >10 per 50 HPF and total
tumor diameter was 17 cm. The localization was unfa-
vorable but bad prognostic signs such as liver or lymph
node metastases were not seen.
Gene expression patterns in GISTs are assessed by
DNA microarray techniques. The technique revealed that
the gene FLJ10261 responsible for encoding the DOG1
protein is specifically expressed in GISTs, irrespective of
KIT or PDGFRA mutation status. However, its function
is not well understood, although it seems to be fairly
specific to GIST and rarely being expressed in other soft
tissue tumors. In future it may play a pivotal role in di-
agnosis of GISTs, especially in PDGFR mutants failing
to express the KIT antigen [20].
5. CONCLUSION
GIST occurrence is not restricted to bowel but can in-
volve unusual sites also and involvement of mesentery
near dudeno-jejunal junction is very rare. The mainstay
of treatment remains surgical resection with adequate
margin. In cases where tumor has malignant potential
based on high mitotic figures on histopathology adjuvent
treatment with tyrosine kinase may prevent or delay re-
lapse. DNA microarray technique may play a vital role in
identifying the gene encoding DOG1 protein in mutants
that does not express KIT antigen and thus may help in
its diagnosis.
6. AUTHOR’S CONTRIBUTIONS
All authors have contributed to patient management,
writing the case report, reviewing and have given the
final approval for publishing the manuscript.
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