Case Report

Carcinoma Arising from Ectopic Pancreas inthe Stomach: Endosonographic Detection ofMalignant Change

Hideki Ura, MD,1 Ryuichi Denno, MD,1 Koichi Hirata, MD, PhD,1 Akiko Saeki, MD,1

Kenichiro Hirata, MD,2 Hiroshi Natori, MD, PhD2

1 First Department of Surgery, Sapporo Medical University School of Medicine, South 1, West 16, Chuo-ku,Sapporo 060, Japan2 Division of Diagnostic Ultrasound and Electronics, Sapporo Medical University School of Medicine,Sapporo 060, Japan

Received 15 May 1997; accepted 10 October 1997

ABSTRACT: We present a case of a submucosal tumorin the stomach that was suspicious for malignancy onpreoperative endosonography. The resected tumorwas histologically diagnosed as a ductal adenocarci-noma that originated in ectopic pancreatic tissue inthe gastric wall. Although malignant transformation inectopic pancreas is extremely rare, it remains an im-portant consideration in the differential diagnosis ofgastric submucosal masses. © 1998 John Wiley &Sons, Inc. J Clin Ultrasound 26:265–268, 1998.

Keywords: ectopic pancreas; malignant transforma-tion; submucosal tumor; endosonography

Ectopic pancreas, also called heterotopic or ab-errant pancreas, is defined as pancreatic tis-

sue lying outside its normal location and lackinganatomic or vascular connections with the pan-creas. This usually asymptomatic condition isfound incidentally at laparotomy or autopsy inthe stomach, duodenum, small intestine, Meckel’sdiverticulum, or biliary tract.1,2 The frequency ofectopic pancreas has been estimated as 1 case per500 explorations of the upper abdomen1 or 0.6–13.7% of autopsies.1–4 Malignant transformationin ectopic pancreatic tissue is extremely rare, andwe found only 14 well-documented cases in ourreview of the literature.5–16 In this report, we de-scribe a case of endosonographically detected ad-enocarcinoma arising from ectopic pancreas inthe stomach.

CASE REPORT

A 60-year-old woman with no medical complaintsunderwent upper gastrointestinal tract radiogra-phy in the course of a mass screening for stomachcancer in March 1993. After a filling defect wasdemonstrated in the upper portion of the stom-ach, she was referred to our hospital for evalua-tion. She had previously undergone surgery forappendicitis but was otherwise healthy. Physicalexamination and routine blood tests were normal.The serum amylase concentration was 71 IU/l(normal, 37–120 IU/l), carcinoembryonic antigenlevel was 1.0 ng/ml (normal, 0–5.9 ng/ml), andcarbohydrate antigen 19-9 level was 12 U/ml (nor-mal, 0–37 U/ml). Gastroscopy showed a smooth-surfaced mass covered with intact mucosa pro-truding into the lumen from the lesser curvaturejust below the cardia. Endoscopic sonography(EUS; GFUM20 scanner, Olympus Optical, To-kyo, Japan) demonstrated an intramural hy-poechoic mass, 18 × 13 mm, with cystic areas (Fig-ure 1A). We advised follow-up in the outpatientclinic because of her asymptomatic status and theminimal risk of malignancy in this small submu-cosal tumor. EUS 1 year later showed no change(Figure 1B). However, a third EUS examination,done 2 years later, revealed that the tumor notonly had increased to 33 × 30 mm but showedextramural growth with marginal irregularity.An enlarged perigastric lymph node (12 × 8 mm)with heterogeneous echogenicity was noted (Fig-ure 1C). These findings aroused a strong suspi-cion of malignant transformation, and the patient

Correspondence to: H. Ura

© 1998 John Wiley & Sons, Inc. CCC 0091-2751/98/050265-04

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underwent surgery in August 1996. At surgery, itwas found that the tumor was partially penetrat-ing the gastric wall and that a few perigastricnodes were enlarged; thus, a proximal gastrec-tomy with regional lymph node dissection wasperformed. The tumor and nodal metastases werecompletely resected. The postoperative coursewas uneventful.

Histologic examination of the resected tumordemonstrated ectopic pancreatic tissue consistingof pancreatic acini, ductal structures, and islets ofLangerhans’ cells within the submucosal layer ofthe stomach, with a gradual transition fromatypical pancreatic duct to frank invasive ductaladenocarcinoma that was well-differentiated and

had widely infiltrated the muscularis propria andsubserosal layers, extending focally to the perito-neal surface (Figure 2). Perineural invasion andlymphatic invasion were present. Metastaseswere found in lymph nodes located along the leftcardia and lesser curvature. A cystic area withinthe tumor, preoperatively demonstrated by EUS,proved to be a dilated pancreatic duct.

DISCUSSION

Ectopic pancreatic tissue in the stomach is mostcommonly found in the antrum and is also seenrelatively frequently along the greater curvature

FIGURE 1. Sonograms obtained endoscopically at a frequency of 12 MHz in April 1993 (A) and March 1994 (B) and at 7.5 MHz in August 1996 (C)

demonstrate a submucosal mass in the stomach. A hyperechoic band indicating the submucosal layer (arrowheads) is interrupted by the mass.Note the preserved serosal interface (open arrow) on A and B. The August 1996 sonogram (C) shows penetration of the tumor in the perigastricfat (white arrows) and a perigastric lymph node (black arrow) with heterogeneous echogenicity.

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and posterior and anterior walls; it rarely occursalong the lesser curvature.17 Malignant change inectopic gastric pancreas was reported in 7 cases inour review of the literature9–11,14–16; 6 of thesetumors were located in the antrum and pyloricregion. In our patient, the tumor was locatedalong the lesser curvature just below the cardia, aparticularly rare location for ectopic pancreas. Oninitial examination, we suspected a myogenic tu-mor such as leiomyoma because it frequently oc-curs submucosally in the upper third of the stom-ach. Although EUS is very useful in depicting theshape and internal structure of tumors, it canrarely predict the histologic diagnosis.18 Thus, wedid not suspect the submucosal mass to be ectopicpancreas until the resected specimen underwentmicroscopic examination. However, swelling of aperigastric node and changes in mass shape andsize as shown by EUS strongly indicated that re-section was necessary.

Histologic determination that a malignant tu-mor has developed from preexisting ectopic pan-creatic tissue may be difficult. Guillou et al15 de-scribed 3 conditions necessary to prove that amalignancy arose from ectopic pancreas: (1) the

tumor must be within or near the ectopic pancre-atic tissue, (2) a direct transition between pancre-atic structures and carcinoma must be observed,and (3) the non-neoplastic pancreatic tissue mustat a minimum comprise fully developed acini andductal structures. Our case satisfied all 3 condi-tions.

Given the small number of reported cases, itremains difficult to predict the behavior of such atumor and to outline a therapeutic strategy. Inthis case, a standard gastrectomy with lymphnode dissection was performed because preopera-tively we had suspected the possibility of malig-nancy. Although malignant transformation in ec-topic pancreas is extremely rare, it remains animportant consideration in the differential diag-nosis of gastric submucosal masses.

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FIGURE 2. Photomicrograph of the tumor shows ectopic pancreatictissue (arrowheads) beneath intact gastric mucosa and invasive pan-creatic-type carcinoma (arrows) arising from the ectopic tissue (he-matoxylin and eosin; original magnification, 20×).

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