ONCOLOGY LETTERS 5: 627-630, 2013
Abstract. Extragastrointestinal stromal tumors (EGISTs) are
neoplasms located outside the gastrointestinal tract in sites
including the omentum, mesentery and retroperitoneum.
EGISTs of the transverse mesocolon are rarely noted in the
literature. Herein, we describe a rare case of giant EGIST
concomitant with gastric cancer in a 78-year-old male who
presented with upper abdominal pain and a palpable mass.
The patient underwent en bloc resection of the tumor with a
distal gastrectomy, with a D2 lymphadenectomy for the gastric
cancer, accompanied with resection of a segment of the trans-
verse colon. The patient received targeted therapy (imatinib
400 mg, daily) and adjuvant chemotherapy with FOLFOX
(six cycles). Neither recurrence nor metastasis was observed
after 24 months of follow-up.
Gastrointestinal stromal tumors (GISTs) are rare neoplasms
that arise from mesenchymal cells of the gastrointestinal tract.
Extragastrointestinal stromal tumors (EGISTs) have no contact
with the stomach and intestine, by definition, and typically
occur in the omentum, mesentery or retroperitoneum (1,2).
However, EGISTs are not connected to the digestive tract (3).
GISTs in the omentum or mesentery are typically metastases
from primary sites within the gastrointestinal tract. EGISTs
are often included in large studies of stromal tumors, in which
they account for less than 10% of overall cases. EGISTs have
rarely been identified in the pancreas, diaphragm, spleen,
pelvis or abdominal wall (4-7).
The most common type of carcinoma associated with
GISTs is gastric carcinoma (8). To the best of our knowledge,
primary EGIST concomitant with digestive tract carcinoma is
rarely encountered. We describe a rare case of giant EGIST
in the transverse mesocolon concomitant with gastric adeno-
carcinoma, in a 78-year-old male who presented with upper
abdominal pain and a palpable mass. We discuss the specific
recommended therapies for patients with concomitant EGST
and gastric cancer, with a review of the literature.
The study was approved by the Ethics Committee of Qilu
Hospital, Shandong University, China. The patient's family
consented to this study.
A 78-year-old male was admitted to hospital for abdominal
distension and pain. The patient had no history of epigas-
tralgia or peptic ulcers and there was no significant relevant
family history. A physical examination revealed a 20x12 cm
palpable mass in the middle and lower abdomen, with minimal
intrinsic mobility. Carcinoembryonic antigen (CEA), cancer
antigen (CA) 724 and carbohydrate antigen (CA) 19-9 levels
were normal. A computed tomography (CT) scan revealed a
21x14 cm heterogeneous mass extending from the fundus to
the mid-abdomen, with a number of solid and cystic compo-
nents within the tumor (Fig. 1A). A gastroscopy revealed an
intraluminal ulcer in the lower posterior wall of the gastric
antrum; biopsy specimens were obtained. No metastatic
lesions were identified in any other organs in either the abdom-
inal ultrasonography or the CT scan. A biopsy confirmed the
presence of an adenocarcinoma of the stomach with poor to
moderate differentiation. A laparotomy revealed an extremely
large tumor (22x15 cm) arising from the transverse mesocolon
and adjacent to the greater curvature of the stomach. The mass
was in close apposition to the pancreas and duodenum. There
was no evidence of invasion or underlying peritoneal infiltra-
tion. The mass was resected en bloc with part of the transverse
colon, and distal gastric resection was performed (Fig. 1B).
Macroscopic examination of the distal gastrectomy
specimen revealed a Borrmann type II tumor in the stomach,
measuring 3x3 cm. On histopathological examination, the
tumor was identified to be an adenocarcinoma with poor to
moderate differentiation that exhibited transmural infiltration
(Fig. 1C). No nerve or vascular invasion was evident. Two lymph
node metastases were detected in 28 retrieved lymph nodes.
According to the TNM classification, the gastric carcinoma
was stage IIIA. Histopathological examination demonstrated
Giant extragastrointestinal stromal tumor in the
transverse mesocolon concomitant with gastric
cancer in an elderly patient: Case report
DONG XUE, HONGQIANG CHEN and YUXIN CHEN
Department of General Surgery, Qilu Hospital, Shandong University, Jinan 250012, P.R. China
Received August 13, 2012; Accepted November 6, 2012
Correspondence to: Dr Yuxin Chen, Department of General
Surgery, Qilu Hospital, Shandong University, 107 Wenhua West
Road, Jinan 250012, P.R. China
Key words: extragastrointestinal stromal tumors, gastric cancer,
XUE et al: GIANT EXTRAGASTROINTESTINAL STROMAL TUMOR CONCOMITANT WITH GASTRIC CANCER
that the extremely large mass was mainly comprised of
epithelioid cells, and revealed focal necrosis, fibrosis and
hemorrhagic areas (Fig. 2A). Mitotic figures were recognized
in 15 out of 50 high-power fields. Immunohistochemical
analysis revealed that CD117 (Fig. 2B) and desmin (Fig. 2C)
were positive in the neoplastic cells. However, tumor cells
exhibited negative expression for CD34, S-100 and smooth
muscle actin (SMA). Based on these results, the diagnosis was
an EGIST of the transverse mesocolon that had not originated
from the digestive tract. The postoperative period of the
patient was uneventful; the patient was discharged two weeks
after surgery. The patient was started on adjuvant chemo-
therapy with a FOLFOX regimen: oxaliplatin IV, 85 mg/m2
(on day 1); leucovorin IV, 200 mg/m2 (on days 1 and 2); 5-FU
(fluorouracil) IV, 400 mg/m2 (on days 1 and 2) and 5-FU IV
22 hours in fusion, 600 mg/m2 (on days 1 and 2). This regimen
was repeated every 2 weeks for 6 cycles. Additionally, the
patient was simultaneously administered imatinib at a dose of
400 mg/day for 1 year. No evidence of tumor recurrence was
identified after 24 months of follow-up.
GISTs identified outside the gastrointestinal tract as apparent
primary tumors are designated as EGISTs. EGISTs may occur
in the omentum, mesentery or retroperitoneum, adjacent to
(although separate from) the stomach and intestine. Their true
origin is uncertain; however, their histological appearance and
immunophenotypes are typically identical to those of classical
GISTs. The EGIST in the present case was located inside the
mesocolon, outside the gastrointestinal tract. EGISTs of the
mesocolon have rarely been noted in the literature (9-11).
The pathogenesis of EGIST concomitant with abdominal
malignancy is still unknown. Only sporadic cases have been
described. EGISTs of the greater omentum (10 and 8 mm in
diameter, respectively) have been identified by coincidence
when a gastrectomy was performed (12). EGISTs are often
asymptomatic as they lack mucosal participation, whereas
GISTs commonly present with gastrointestinal or intratumoral
bleeding (13,14). Due to their their anatomic site, EGISTs
typically grow larger than GISTs and only present clinical
symptoms after a significant period of time (15,16). Certain
studies have described gastric stromal tumors to be synchro-
nous with gastric malignancy. To the best of our knowledge,
a giant EGIST in the transverse mesocolon concomitant with
gastric carcinoma has never been studied.
The clinicopathological or immunohistochemical features
of EGISTs and GISTs were not observed to be markedly
different. Primary EGISTs of the omentum and mesentery
demonstrated clinicopathological and immunohistochemical
characteristics similar to a GIST of the digestive tract
described previously in the literature (17). This supports the
hypothesis that these tumors originate from extragastroin-
testinal c-kit positive cells. Their histogenesis, criteria for
diagnosis, prognostic factors and classification have been
debatable and controversial. GISTs are accurately diagnosed
Figure 1. (A) Abdominal computed tomography (CT) scan showing a heterogenous mass occupying most of the middle and lower abdomen. (B) The mass, part
of the transverse colon and the distal stomach were resected en bloc. (C) Pathologic sections of the gastric adenocarcinoma with poor to moderate differentia-
tion (hematoxylin and eosin stain, x200).
Figure 2. (A) The tumor is mostly composed of epithelioid cells with focal necrosis, fibrosis and hemorrhagic areas (hematoxylin and eosin staining, x200).
(B) Immunohistochemically, the epithelioid cells demonstrated cytoplasmic staining for CD117 (c-kit) (x200). (C) Immunohistochemically, the epithelioid
cells demonstrated cytoplasmic staining for desmin (x200).
ONCOLOGY LETTERS 5: 627-630, 2013
by their morphology and immunophenotyping. Histologically,
there are three types of GISTs: spindle, epithelioid and mixed.
The diagnosis of an EGIST in the present case was in accor-
dance with the histological and immunohistochemical criteria;
the tumor was epithelioid-type, and was immunopositive for
CD117 and desmin. More than 95% of EGISTs express CD117,
the c-kit proto-oncogene protein that is a transmembrane
receptor for the stem cell growth factor; while 50-100%
express CD34, the human progenitor cell antigen. It is less
common for EGISTs to stain positively for SMA, S-100 and
desmin (6,17,18). Zheng et al demonstrated that the c-kit and
PDGFRA mutation in EGISTs was similar to that of GISTs.
Therefore, from a molecular genetics perspective, EGISTs
may be a unique subtype of GISTs (3).
The risk categories of EGISTs are contested. A tumor
size >10 cm, mitotic activity >2 per 50 high-power fields,
tumor necrosis, marked nuclear atypia, >10% Ki-67 protein
expression and epithelioid-/mixed cell-type, have acted as
significant predictors of survival (2,3). Survival analysis
indicated that mitotic count and Ki-67 protein expression
levels were significant predictors of disease-specific survival;
however, tumor size, primary location, c-kit and PDGFRA
gene mutations were not. The high risk of recurrence and
prognostic factors for survival are controversial. This may be
due to a limited number of samples, a different composition of
ages and different histologic judgements of pathologists across
studies. Therefore, it is necessary to enlarge the sample size
in order to reach a precise conclusion. EGISTs are capable
of remaining clinically silent, irrespective of their large size,
which exceeded 10 cm in the majority of published cases.
EGISTs are rarely encountered due to the fact that they
seldom produce symptoms that would lead to their detection.
Tumor size has not been observed to be a reliable prognostic
parameter in EGISTs. In the present case, focal necrosis, >10%
Ki-67 protein expression and a high-power mitotic count >10
resulted in the tumor being considered high-risk. The tumor
in the present case demonstrated epithelioid-type histology.
Positive immunohistochemical staining for CD117 is also
a defining feature of EGISTs, and it correlates with a tumor
response to treatment with the KIT kinase activity inhibitor.
The present case demonstrated strong positive staining for
CD117 and desmin, as well as negative staining for CD34,
S-100 and SMA, by immunohistochemistry. We propose that
tumor coexistence is a unique event in histology.
There are few data regarding the clinicopathological
factors of EGISTs that predict the patient's prognosis. In
a study by Reith et al, 39% of patients with EGISTs had an
adverse outcome, which suggested that EGISTs were aggres-
sive and were more similar to GISTs located in the distal
gastrointestinal tract (2). Barros et al analyzed 9 EGISTs and
revealed that the average overall survival was 26.4 months (6).
Llenas-García et al demonstrated that 66.6% of mesenteric
cases with a high mitotic rate exibited hepatic metastasis at 6
and 32 months, respectively (17). It was suggested that EGISTs
that originated from a mesenteric location had an aggressive
course that was more similar to that of small intestinal, as
opposed to gastric stromal tumors.
Surgery is the standard treatment for non-metastatic
EGISTs. A preoperative diagnosis is difficult, and the patient
undergoes an operation based on the diagnosis of an abdom-
inal mass. Where possible, en bloc resection with contiguous
tissues and regional lymph nodes is conducted. It is crucial for
the pathologist to examine whether the tumor is adhesive to
the gastrointestinal wall or other tissues. A histological diag-
nosis of EGIST is often unsatisfactory. In the present case, the
patient underwent an en bloc resection of the tumor and partial
transverse mesocolon, accompanied with a distal gastrectomy
with a D2 lymphadenectomy. Positive immunohistochemical
staining for CD117 is a defining feature of EGISTs. C-kit-
positive tumors are most responsive to treatment with a c-kit
selective tyrosine kinase inhibitor. Due to the advent of targeted
therapy, imatinib, an inhibitor of the tyrosine kinase activity
of c-kit, has revolutionized the treatment of this disease.
The recommended first-line treatment of advanced GIST is
400 mg/day imatinib (19). In certain patients, an escalated
dose (800 mg/day) has achieved tumor control and conferred
further survival benefits after failure with 400 mg/day (20).
Adjuvant chemotherapy (FOLFOX) and imatinib were applied
in the present case. The patient was followed up and was free
of recurrence 24 months after surgery.
The coexistence of EGIST with other abdominal malignan-
cies is a rare phenomenon; we suggest that their synchronous
occurrence may be a coincidence. Although there are data
regarding the co-occurrence of EGISTs and other malignant
tumors, the mechanism of synchronous tumorigenesis remains
unclear. Surgical resection is currently the mainstay of treat-
ment for EGISTs. The existing data on the coexistence of
EGISTs with other types of gastric carcinoma are insufficient
to reach a final conclusion regarding the treatment, prognosis
In summary, the present case was a giant EGIST in the
mesocolon accompanied with gastric cancer in an elderly
male. We stress that, although their prevalence is very low,
surgery-based multimodal treatment is the preferred strategy
for compound tumors. Adjuvant chemotherapy and targeted
therapy are important for high-risk EGISTs accompanied with
digestive tract malignancies. Due to the limited number of
cases, the existence of a common tumorigenesis factor among
the different tumors cannot be identified. Further studies are
required to expound the possible association.
The authors would like to thank Mr. Xinjun Li for critically
reading the manuscript.
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