Heterotopic Pancreatic Pseudocyst Radiologically Mimicking Gastrointestinal Stromal Tumor

Abstract

Heterotopic pancreas is a relatively common variant of foregut embryologic dystopia that can be described as pancreatic tissue found outside the normal anatomic location, being independent from vascular supply of normal pancreas. Having all features of pancreatic tissue except for the major duct structures, this ectopic tissue may be clinically recognized when pathologic changes take place. Inflammation, hemorrhagic or obstructive states, and eventually malignancy-related problems may become a diagnostic challenge for clinician and finally lead to consequences of misdiagnosis. In this article we will discuss a case of heterotopic pancreatic tissue located in gastric cardia, which was diagnosed preoperatively as gastrointestinal stromal tumor.

Full text

Int Surg 2015;100:486–489
DOI: 10.9738/INTSURG-D-13-00242.1
Heterotopic Pancreatic Pseudocyst
Radiologically Mimicking Gastrointestinal
Stromal Tumor
Dauren Sarsenov
1
, Mehmet B ¨
ulent Tırnaksız
1
, Ahmet B ¨
ulent Do˘
grul
1
,¨
Ozlem Tanas
2
G¨
okhan Gedikoglu
2
, Osman Abbaso˘
glu
1
1
Department of General Surgery, Hacettepe University Faculty of Medicine, Ankara, Turkey
2
Department of Pathology, Hacettepe University Faculty of Medicine, Ankara, Turkey
Heterotopic pancreas is a relatively common variant of foregut embryologic dystopia that
can be described as pancreatic tissue found outside the normal anatomic location, being
independent from vascular supply of normal pancreas. Having all features of pancreatic
tissue except for the major duct structures, this ectopic tissue may be clinically
recognized when pathologic changes take place. Inflammation, hemorrhagic or
obstructive states, and eventually malignancy-related problems may become a diagnostic
challenge for clinician and finally lead to consequences of misdiagnosis. In this article
we will discuss a case of heterotopic pancreatic tissue located in gastric cardia, which was
diagnosed preoperatively as gastrointestinal stromal tumor.
Key words: Ectopic pancreas Pseudocyst Gastrointestinal stromal tumor Misdiagnosis
Heterotopic (ectopic) pancreas is defined as the
presence of pancreatic tissue in an aberrant
site that is not anatomically and vascularly connect-
ed to the pancreas proper.
1,2
Ectopic pancreatic
tissue is most commonly found in the duodenum
(particularly the second portion), ampulla, stomach
(prepyloric antrum), and upper jejunum; it can also
occur in the liver, biliary tract, Meckel’s diverticu-
lum, and several other sites such as large bowel,
spleen, omentum, mediastinum, lung, thyroid, and
even brain.
1–6
The heterotopic pancreatic tissue is
usually located in the submucosa and/or the
muscularis or subserosa.
1,2,4
Practically any pancreatic pathology can also
occur in the heterotopic pancreatic tissue including
acute pancreatitis and neoplastic transformation.
1,4,7,8
Episodes of acute pancreatitis may cause local
inflammation and typical pancreatitis-related com-
Corresponding author: Mehmet B ¨
ulent Tırnaksız, MD, Hacettepe University Faculty of Medicine, Department of General Surgery,
Sıhhiye, Ankara, Turkey.
Tel.: 9031233051677 or 905337171038; Fax: 903123104071; E-mail: mbulent@hacettepe.edu.tr
486 Int Surg 2015;100

plications in the host organ. The ectopic pancreatic
tissue can lead to ulceration and bleeding in the cases
located beneath a mucosa. Being a mass-forming
lesion, it may also result in luminal obstruction
(particularly in the prepyloric antrum).
1,4
Although it is a relatively common congenital
anomaly (0.5% to 13% in autopsy series), in most
cases heterotopic pancreas remains clinically silent
and is found incidentally during surgery or an
endoscopic and/or radiological investigation.
1,9
Heterotopic pancreas may be confused with other
solid tumors of the host organ.
Heterotopic pancreas in the stomach is usually
located in the prepyloric area.
10
We report here an
unusual case of heterotopic pancreas with a pseu-
docyst formation in the gastric cardia mimicking
gastrointestinal stromal tumor.
Case Report
A 44-year-old male presented with a two month
history of abdominal pain, nausea, and vomiting. The
pain was intense in the mid-epigastric region and
radiated to all over the abdomen and had no relation
with meals. The patient denied any weight loss
during this time period. Physical examination
showed normal findings. Routine blood tests includ-
ing serum alfa fetoprotein, CA 19-9, and carcinoem-
briyonic antigen levels were within normal limits.
One week before admission to our hospital the
patient undertook a computerized tomography with
oral and intravenous contrast which showed a 4.8 3
4.9 34.3 cm well-defined mass lesion on the lesser
curvature in the gastric cardia with no evidence of
local invasion (Fig. 1). The lesion was in close
proximity with the left lobe of liver. The patient
was referred to us for further treatment. An endo-
sonographic study at our hospital revealed a 4.3 cm
diameter hypoechoic lesion located on the lesser
curvature of the stomach just below the esophago-
gastric junction and a gastrointestinal stromal tumor
was suspected. A decision was made to proceed with
surgery. On exploration, an exophytic cystic lesion
measuring 6 35 cm was identified on the anterior
wall of the stomach in the cardia region. The
pancreas was found to be normal and no other
intra-abdominal pathology was detected. The lesion
was surrounded by a mild inflammatory reaction
which produced adherence to the hepatogastric
ligament and the left lobe of liver. The lesion
appeared to infiltrate serosa but not the muscularis
propria and mucosa and was not infiltrating the
surrounding tissue. During the dissection of the
lesion the cyst cavity was opened and approximately
40 ml of creamy white fluid aspirated for further
analysis. The lesion’s anterior wall was excised
completely. The gastric wall underneath the lesion
appeared to be intact; there was no gross involve-
ment of the mucosa. Since the lesion appeared benign
and nonneoplastic we decided not to perform gastric
resection. Unfortunately, the frozen section examina-
tion was not available at the time of the surgery. The
patient did have an uneventful postoperative period
and was discharged 5 days after surgery. He has
remained free of symptoms with negative endoscopic
and computerized tomographic findings since then.
Biochemical study of the diluted (1/10) aspirate
revealed high levels of pancreatic amylase (1422 U/L).
Histopathologic examination of the resected lesion
showed pancreatic tissue with acinar cells and dilated
ducts located subserosally (Fig. 2A and 2B). The
ductal epithelia and acinar cells were positively
stained with antibodies against cytokeratin 19 (Fig.
2C).
11
The pathologic diagnosis was heterotopic
pancreatic tissue with pseudocyst formation.
Discussion
Pancreatic heterotopia is often an incidental find-
ing.
1,12
It is generally asymptomatic, but it may
cause symptoms when complicated by inflamma-
tion,
7
ulceration, hemorrhage,
13
obstruction,
4
or
Fig. 1 Well circumscribed, hypodense lesion radiologically
considered to be a gastrointestinal stromal tumor. Arrows
delineate outer borders of the tumor.
ECTOPIC PANCREAS PSEUDOCYST SARSENOV
Int Surg 2015;100 487

malignant transformation.
8
Ectopic pancreatic tissue
in the stomach is usually found in the prepyloric
area.
10
Ectopic pancreas in the gastric cardia has
been rarely reported.
10,14,15
In majority of cases it is
buried in submucosal layer of the gastric wall.
2
In
the presented patient, the ectopic pancreatic tissue
was located in the cardia and largely the subserosal
layer and partially muscularis propria of the
stomach were involved. The gastric ectopic pancre-
atic tissue may cause abdominal pain, nausea, and
vomiting, as in our case.
12
Cystic changes can be seen in the ectopic
pancreatic tissue.
7,16–18
If there is no communication
between the ectopic tissue and the gastric lumen,
retention of the exocrine secretions may result in
cyst formation. Retention cysts are usually small
(less than 1–2 cm in size) and lined by a single layer
of normal epithelium; whereas, pseudocysts are
usually bigger and their wall lacks epithelial
lining.
19
In our case, the cyst was devoid of
epithelial lining and also mild inflammation was
found around the cyst. Therefore, we thought that it
was more likely a pseudocyst.
Endoscopic ultrasonography (EUS) and comput-
erized tomography (CT) are frequently used for the
diagnosis of gastric submucosal mass lesions.
Because gastrointestinal stromal tumor (GIST) is
the most common gastric submucosal mass lesion,
heterotopic pancreas is usually confused with GIST
at EUS or CT.
20
It is difficult to distinguish ectopic
pancreas from gastric GIST at CT or EUS, because
there are no characteristic findings of ectopic gastric
pancreas.
15,21,22
However, recent studies
23,24
have
suggested that combined use of some imaging
features (endoluminal growth pattern, ill-defined
border, and prepyloric location) of gastric ectopic
pancreas can help distinguish it from GIST. In our
case, both CT and EUS misdiagnosed the ectopic
pancreatic tissue as a GIST that underwent degen-
eration. Presence of a well-defined border, exophytic
growth pattern, and proximal gastric location of the
lesion led to radiologist interpret the lesion as
gastric GIST.
Asymptomatic ectopic pancreas does not require
treatment in the presence of a histopathologic
diagnosis. However, it is difficult to obtain a tissue
diagnosis of heterotopic pancreas without an oper-
ative intervention and therefore in most cases a
surgical removal of the lesion is unavoidable.
Symptomatic patients should undergo surgery both
to obtain tissue diagnosis and for symptom relief.
Surgery can be performed by using open or
minimally invasive techniques depending on the
location and size of the lesion. In the present patient,
due to proximal location and size of the lesion we
decided to proceed with open surgery.
In conclusion, preoperative diagnosis of gastric
ectopic pancreas remains challenging. In this case
report we demonstrated a gastric ectopic pancreas
with an atypical appearance and location.
Acknowledgments
There is no financial support or conflict of interest
for this study.
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