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Ectopic Pancreatic Tissue

Published on 19/07/2015 by admin

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Last modified 22/04/2025

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 Well-defined, smoothly marginated, round/oval submucosal mass with central umbilication

image Reflux of contrast into rudimentary duct-like structure may extend below central pit
• CT findings

image Often too small to be detected
image Round or oval mass with protrusion into gut lumen
image May have well-defined or ill-defined margins on CT
image Enhancement pattern is variable

– Acini-dominant ectopic pancreas shows homogeneous, avid enhancement
– Others types more heterogeneous (or even cystic)
– Overlying mucosa of bowel often avidly enhancing
• MR findings: Ectopic pancreas is isointense on all pulse sequences with main pancreas (including DWI/ADC)

TOP DIFFERENTIAL DIAGNOSES

• Gastric GIST
• Other gastric hypervascular submucosal lesions (glomus tumor, carcinoid, GIST)
• Gastric ulcer
• Gastric carcinoma
• Gastric metastases and lymphoma

CLINICAL ISSUES

• Most patients are asymptomatic and ectopic pancreas is usually an incidental finding
• Can be complicated by bleeding or mucosal ulceration and patients present with epigastric pain and melena
• Can undergo any of the inflammatory or neoplastic abnormalities of main pancreas including acute/chronic pancreatitis and development of malignancy
image
(Left) Axial CECT demonstrates a mural mass image in the body of the stomach. Note that the mass enhances similarly to the normal pancreas. Endoscopic biopsy revealed ectopic pancreatic tissue.

image
(Right) Axial CECT in a patient with abdominal pain demonstrates a cystic intramural mass image within the distal stomach, found to represent ectopic pancreas after surgery. Ectopic pancreas can appear homogeneous, heterogeneous, or cystic depending on its internal mixture of acini, ducts, and islet cells.
image
(Left) Upper GI series spot film shows a small antral mass with intact mucosa. A central “dot” of barium image can be seen filling a rudimentary duct.

image
(Right) Upper GI image shows a small, smooth, intramural mass image along the greater curvature of the antrum without central umbilication. Only 45% of patients with ectopic pancreas will have central umbilication on a barium study. In the absence of this sign, it is difficult to distinguish ectopic pancreas from other intramural masses, such as metastasis or GIST.

TERMINOLOGY

Abbreviations

• Ectopic pancreatic tissue (EPT)

Synonyms

• Pancreatic rests; heterotopic, aberrant, accessory pancreas

Definitions

• Pancreatic tissue located outside of normal confines of pancreas and lacking any anatomic or vascular connection with main pancreas

IMAGING

General Features

• Best diagnostic clue

image Small submucosal gastric mass with central umbilication 

– Central umbilication (45% of cases): Orifice of rudimentary duct through which ectopic pancreatic tissue (EPT) drains into gastric lumen
• Location

image 90% of all cases found in upper GI tract (stomach, duodenum, or proximal jejunum)

– Most commonly gastric antrum (< 6 cm from pylorus)
– Can rarely arise in ileum, Meckel diverticulum, liver, biliary tract, spleen, omentum, mesentery, lung, mediastinum, fallopian tube, esophagus, colon
image Primarily arise in submucosa (73%); can also be located in muscular layer (17%) or subserosa (10%)

– 2nd most common gastric submucosal mass (behind only mesenchymal lesions such as GI stromal tumors)
• Size

image Nodule: 0.5-2 cm; may be up to 5 cm in diameter
image Pit: May be 5 mm in diameter and 10 mm in length
• Morphology

image Submucosal layer: Appears as well-defined flat or nodular projection into gut lumen with intact overlying mucosa
image Muscularis or subserosal layers: Produces smooth bulge or area of wall thickening

Radiographic Findings

• Ability to visualize EPT depends on size/location of deposit
• Well-defined, smoothly marginated, round or oval submucosal mass with central umbilication

image Typically 1-2 cm in diameter, along greater curvature or posterior aspect of antrum, and within 6 cm of pylorus
image Nodule may be larger, narrow-based, and polypoid in appearance, or located in more proximal antrum
• Central umbilication is a specific feature: Central depression with contrast filling pit in center of mound

image May be mistaken for ulcerative lesion
image Reflux of contrast into rudimentary duct-like structure may extend below central pit
• Upper GI series may show narrowed pyloric channel ± polypoid or sessile mass

CT Findings

• Often too small to be detected on CT
• Round or oval mass with tendency for endoluminal growth (protrusion into gut lumen)

image May have well-defined or ill-defined margins
• Enhancement pattern is variable

image Acini-dominant ectopic pancreas shows homogeneous, avid enhancement
image Others types with mixture of acini and ducts may appear more heterogeneous (and sometimes even cystic)
image Overlying mucosa avidly enhancing as a result of inflammation
• Central umbilication not typically visualized on CT

MR Findings

• Isointense on all pulse sequences with main pancreas

Other Modality Findings

• Endoscopy: More capable of identifying EPT when nodule is small and located in duodenum

image Often nonspecific finding due to submucosal location
image Central umbilication may be visualized, and, if injected, rudimentary duct system may be seen

DIFFERENTIAL DIAGNOSIS

Gastric Ulcer

• Round ulcer, smooth mound of edema, radiating folds to ulcer edge, Hampton line, ulcer collar

Gastric GIST

• Primary differential diagnosis on CT/MR
• Submucosal mass with frequent ulceration, tendency for exophytic growth, and variable enhancement on CT/MR

Other Gastric Hypervascular Submucosal Lesions

• Glomus tumor, carcinoid tumors, and some GISTs appear as hypervascular masses on CT/MR within submucosa

Gastric Carcinoma

• Polypoid or circumferential mass, ± ulceration, focal wall thickening with mucosal irregularity

Gastric Metastases and Lymphoma

• May show bull’s-eye sign: Ulceration in center of lesion
• Melanoma, Kaposi sarcoma, lymphoma (often multiple)

PATHOLOGY

General Features

• Seen in organs, like pancreas, derived from endoderm as result of heteroplastic differentiation of embryonic endoderm parts that do not normally produce pancreatic tissue

Microscopic Features

• May contain all or only some elements of normal pancreas, including acini, ducts, and islet cells

CLINICAL ISSUES

Presentation

• Most patients are asymptomatic: Incidental finding
• Most common symptoms: Epigastric pain and melena

image May cause symptoms of pyloric obstruction when located in stomach
image Periampullary lesions may rarely cause biliary obstruction

Demographics

• Epidemiology

image Incidence of autopsy series: 2-14%
image Incidence of incidental identification at laparotomy: 0.2%

Natural History & Prognosis

• Often complicated by bleeding or mucosal ulceration
• Can undergo any of the inflammatory or neoplastic abnormalities of main pancreas

image Acute or chronic pancreatitis ± typical complications
image Development of ductal adenocarcinoma

Treatment

• Surgical intervention for obstruction or hemorrhage
• Endoscopic resection if lesion confined to submucosa
• May be treated expectantly when asymptomatic

DIAGNOSTIC CHECKLIST

Consider

• If central umbilication is absent, lesion may not be differentiated from other submucosal tumors
image
Sagittal reformation of CECT shows a mural mass image to have broad base of attachment to the gastric wall and to have obtuse angles with the gastric lumen, suggesting a likely submucosal location for the mass. Endoscopic biopsy revealed ectopic pancreatic tissue.

image
Upper GI spot film shows a small intramural polypoid mass with a central collection of barium image, which is essentially diagnostic of ectopic pancreatic tissue. The central barium collection represents the rudimentary pancreatic duct.
image
Upper GI along the greater curvature of the antrum shows a small intramural polypoid mass with a central collection of barium image, which is essentially diagnostic of ectopic pancreatic tissue. The central barium collection represents the rudimentary pancreatic duct.
image
Upper GI along the greater curvature of the antrum shows a small intramural polypoid mass with a central collection of barium image, which is essentially diagnostic of ectopic pancreatic tissue. The central barium collection represents the rudimentary pancreatic duct
image
Upper GI shows a small mass image along the greater curvature of the antrum. The mass has almost right angle interface with the gastric wall and smooth overlying mucosa, characteristic of an intramural mass. Note the central tract of barium image filling the rudimentary pancreatic duct, establishing the diagnosis of ectopic pancreas.
image
Upper GI demonstrates a small intramural mass image along the greater curve of the stomach. The overlying mucosa is smooth. The size, location, and appearance of this lesion are typical of ectopic pancreas.
image
Upper GI shows a small, smooth, intramural mass image along the greater curvature of the antrum. No central umbilication is noted. Only 45% of patients with ectopic pancreas will have a central umbilication demonstrated on a barium study. In the absence of this sign, it is difficult to distinguish ectopic pancreas from other types of intramural masses, such as metastasis or a primary stromal tumor.
image
Upper GI shows a small mass along the greater curvature of the antrum. The mass has almost right angle interface with the gastric wall and smooth overlying mucosa, characteristic of an intramural mass. Note the central tract of barium image filling the rudimentary pancreatic duct, establishing the diagnosis of ectopic pancreas.
image
Upper GI spot film shows a small mass with central umbilication image. This is an unusual location for an ectopic pancreas. A “bull’s-eye” lesion of this type and location would raise concern for a metastatic lesion, Kaposi sarcoma, or lymphoma.

SELECTED REFERENCES

1. Jang, KM, et al. Ectopic pancreas in upper gastrointestinal tract: MRI findings with emphasis on differentiation from submucosal tumor. Acta Radiol. 2013; 54(10):1107–1116.

 

Kalaitzakis, E, et al. Gastric ectopic pancreas: not always an innocent bystander. JOP. 2013; 14(6):684–685.

O’Malley, RB, et al. Case of the season: ectopic pancreas. Semin Roentgenol. 2013; 48(3):188–191.

Hur, BY, et al. Gastroduodenal glomus tumors: differentiation from other subepithelial lesions based on dynamic contrast-enhanced CT findings. AJR Am J Roentgenol. 2011; 197(6):1351–1359.

Wei, R, et al. Upper gastrointestinal tract heterotopic pancreas: findings from CT and endoscopic imaging with histopathologic correlation. Clin Imaging. 2011; 35(5):353–359.

Kim, JY, et al. Ectopic pancreas: CT findings with emphasis on differentiation from small gastrointestinal stromal tumor and leiomyoma. Radiology. 2009; 252(1):92–100.

Nijs, EL, et al. Congenital and developmental pancreatic anomalies: ultrasound, computed tomography, and magnetic resonance imaging features. Semin Ultrasound CT MR. 2007; 28(5):395–401.

Mortelé, KJ, et al. Multimodality imaging of pancreatic and biliary congenital anomalies. Radiographics. 2006; 26(3):715–731.

Yu, J, et al. Congenital anomalies and normal variants of the pancreaticobiliary tract and the pancreas in adults: part 2, Pancreatic duct and pancreas. AJR Am J Roentgenol. 2006; 187(6):1544–1553.

Nijs, E, et al. Disorders of the pediatric pancreas: imaging features. Pediatr Radiol. 2005; 35(4):358–373. [quiz 457].

Benya, EC. Pancreas and biliary system: imaging of developmental anomalies and diseases unique to children. Radiol Clin North Am. 2002; 40(6):1355–1362.

Jeong, HY, et al. Adenocarcinoma arising from an ectopic pancreas in the stomach. Endoscopy. 2002; 34(12):1014–1017.

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