| Keywords
EUS, ectopic pancreas, pancreatitis, submucosal
gastric mass
Introduction
The occurrence of heterotopic pancreatic
tissue is uncommon, ranging in frequency from 0.6% to 14%
in autopsy studies.(1-2) It is defined as the presence of
aberrant pancreatic tissue that lacks vascular, neural, and
anatomical continuity with the pancreas.(3-4) When present,
heterotopic pancreatic tissue is generally asymptomatic, and
therefore often discovered as an incidental finding. Pancreatic
heterotopia has been reported to be complicated by ulceration,
bleeding, inflammation within the rest (pancreatitis), and
rarely, malignant degeneration.(3,5-9) We report an unusual
case of symptomatic pancreatic heterotopia.
Methods for EUS Capture
Upper GI Endoscopy and endoscopic ultrasound
were performed with a Pentax video gastroscope and an endosonoscope.
The endosonoscope provided EUS images at a frequency of 5mHz
on a Hitachi 525 console. Digital images were captured with
an 'in-line' video capture board and processed with Adobe
Photoshop.
Case/Body
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Figure
1 |
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Figure
2 |
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Figure
3 |
A 30-year old female with a history of right-sided
colon cancer previously treated with right hemicolectomy and
adjuvant chemotherapy was referred for evaluation of new onset,
sharp, intermittent epigastric pain, nausea, and hyperamylasemia.
A computerized axial tomography study (CT)
of the abdomen (Figure 1) demonstrated a 2.5 cm complex mass
arising from the posterior wall of the gastric antrum. Mesenteric
stranding was present adjacent to the mass, suggestive of
an inflammatory component (Figure 2). The liver, spleen, pancreas
and kidneys appeared normal.
After the CT, the patient underwent an esophagogastroduodensocopy
(EGD), which demonstrated a large mass in the gastric antrum
that appeared to be submucosal (Figure 3). Extrinsic compression
was noted in the duodenum. Endoscopic ultrasound (EUS) was
performed to further evaluate the mass. EUS revealed a large
heterogenous mass arising from the antrum and extending through
the gastric serosa into the surrounding tissue. A fine needle
aspiration of the mass was performed. EUS images are shown
below (Figures 4 and 5).
Cytologic examination of the aspirate taken
from the mass was nondiagnostic and the patient was referred
for surgical treatment.
At surgical resection an inflammatory gastric
mass was noted adjacent to the pylorus with surrounding adenopathy.
A vagotomy and antrectomy were performed. Examination of the
peritoneal cavity and liver revealed no evidence of metastatic
disease.
Review of the histology provided by frozen
sections demonstrated heterotopic pancreatic tissue with surface
ulceration, fibrosis, and chronic inflammation.
Discussion/Summary
Statement
The differential diagnosis for a submucosal
gastric mass in a patient with this history would include
a gastrointestinal stromal cell tumor, gastric metastasis,
and a pancreatic heterotopia. The characteristic endosonographic
appearance of a stromal cell tumor includes well-defined borders,
a homogenous internal structure, and an intramural location.
The subserosa or serosa (the outer hypoechoic layer) should
be seen covering the mass. With malignant transformation,
the tumor may demonstrate echo-dense foci, echo-poor areas
representing tissue necrosis, or both. Malignant submucosal
tumors include leiomyosarcoma, malignant leiomyoblastoma,
and Kaposi?s sarcoma. These tumors are typically >3 cm
in size, have a heterogenous echogenicity that frequently
obliterate the normal echotexture of the gastric wall, and
invade the serosa and subserosa.
Pancreatic heterotopia may be accurately
diagnosed by their endoscopic appearance alone. At endoscopy
the lesion may appear as a small, sessile gastric lesion with
a central invagination along the greater curvature of the
gastric antrum or, more commonly, as a shallow crater-like
depression of the gastric wall. Biopsies with cold forceps
may demonstrate pancreatic tissue. On EUS the echotexture
may have a variable appearance with a regular hypoechoic echopattern
or may demonstrate a central primitive duct system. They are
generally confined to the submucosa although involvement of
the serosa and subserosa has been reported.(4)
It is unusual to see heterotopic pancreatic
tissue of this magnitude. The endosonographic appearance of
the mass in this patient was suggestive of malignancy because
of the invasion of surrounding structures and the presence
of complex echo patterns. The suspicion was strong for metastatic
colon cancer recurrence prior to surgical exploration. However,
this mass was not demonstrated to be malignant on surgical
resection but proved to be an inflammatory mass due to acute
pancreatitis within a large focus of pancreatic heterotopic
tissue. The head, body, and tail of the pancreas were completely
normal by CT, EUS, and surgical inspection. The patient's
abdominal pain and nausea were caused by acute pancreatitis
occurring within this large heterotopia and she experienced
complete resolution of symptoms post-operatively.
References
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Gastric heterotopic pancreas: a case report and review
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