Heterotopic pancreas in the jejunum: highlighting the necessity of excision and histopathological confi rmation – a case report

Overview

Heterotopic pancreas (HP) is a congenital anomaly characterized by the presence of pancreatic tissue that is anatomically separate from the main pancreatic gland without continuity of the duct system and vascularity. The most frequent locations for this displacement are within the upper gastrointestinal tract, particularly in the stomach, duodenum, and proximal jejunum. Other less common sites include the esophagus, ileum, Meckel diverticulum, biliary tree, mesentery, and spleen. Typically, uncomplicated heterotopic pancreas does not exhibit symptoms, and the lesion is often discovered incidentally during unrelated surgeries, imaging examinations, or autopsy. This report describes a 35-year-old male with a history of corrosive ingestion who presented with dysphagia. During surgical exploration, a tissue measuring 0.7 × 0.5 cm was observed approximately 40 cm from the DJ flexure in the jejunum. The identified tissue was excised and sent in for histopathological examination (HPE). In conclusion, we advise the excision of the ectopic tissue and recommend HPE because the diagnosis of HP cannot be confirmed without a thorough histopathological examination. Despite its rarity, heterotopic pancreas should be included in the differential diagnosis when evaluating gastrointestinal stromal tumors.

Keywords:

ectopic – pancreas – chronic pancreatitis – dysphagia – endoscopy

Introduction

A congenital anomaly, termed heterotopic pancreas (HP), results in the physical differentiation of pancreatic tissue from the main pancreatic gland. HP refers to pancreatic tissue located in areas outside its typical anatomical position [1]. This alteration predominantly occurs in the upper gastrointestinal tract, notably in the stomach, duodenum, and proximal jejunum. Less common sites include the esophagus, ileum, Meckel‘s diverticulum, bile duct, mesentery, and spleen [2].

Determining the accurate incidence of HP poses challenges due to the asymptomatic nature of most affected individuals. Autopsy findings suggest a prevalence ranging from 0.5% to 13.7%. Incidentally, the condition is encountered in approximately 0.2% of upper abdominal surgeries and 0.9% of gastrectomies [3].

Despite its infrequent manifestation of symptoms, it is often discovered incidentally during laparotomy. Despite advancements in diagnostic technology, differentiating it from a tumor remains challenging for medical professionals. Hence, we are presenting a case report on a 35-year-old male patient with a heterotopic pancreas, where dysphagia is a prominent symptom.

Case presentation

A 35-year-old male, without known comorbidities, was admitted to our institution, presenting with dysphagia. The patient had a history of caustic ingestion and was previously diagnosed with post-corrosive intake esophagitis, esophageal stricture, and gastritis based on an upper GI scope conducted externally. The scope revealed a benign stricture with luminal compromise at 35 cm beyond the scope passage (Fig. 1).

The patient‘s vital signs were stable upon examination, and there were no other positive clinical findings. All routine biochemical and hematological investigations were conducted, and the results were within normal limits. The patient was scheduled for feeding jejunostomy for enteral nutrition, and the associated risks were explained.

During surgery, a tissue measuring 0.7 × 0.5 cm was observed approximately 40 cm from the DJ flexure in the jejunum. The tissue was excised (Fig. 2) and sent in for histopathological examination (HPE). Histological examination revealed ectopic pancreatic tissue within the gastric muscularis layer, encompassing excretory ducts, acini, and islet cells (Fig. 3–5). Chronic pancreatitis indicators were evident, such as fibrosis and dilated ducts filled with proteinaceous material. Additionally, an abscess was identified, suspected to be an ectopic pancreas associated with focal acute pancreatitis within the ectopic tissue.

Discussion

Jean Schulz was the first to document HP in 1727 when it was observed in an ileal diverticulum. Subsequently, in 1859, Klob identified the histological characteristics of HP [4]. HP, also known as ectopic pancreas or accessory pancreas, refers to a congenital anomaly where pancreatic tissue is situated at a distance from the main pancreatic gland without the presence of continuous blood vessels or ducts. It is also termed pancreatic chorio or adenomyoma [5].

The embryological explanation for HP remains uncertain, although the misplacement theory is widely accepted. According to this theory, discrete deposits of pancreatic tissue become detached from the main pancreatic body and migrate into the developing gastrointestinal system. Alternatively, the metaplastic theory suggests that endoderm tissue migrates to the submucosa, where it transforms pancreatic tissue during embryonic development. However, the totipotent cell theory proposes that pancreatic tissue originates from the differentiation of endoderm cells that line the gut [6].

The actual frequency of HP remains uncertain since many patients don‘t show symptoms. Typically, HP is only discovered incidentally during surgeries performed for other reasons. When symptoms do arise due to local inflammation, patients may experience abdominal pain, pancreatitis, gastrointestinal bleeding, intestinal obstruction, or perforation. There have been rare cases of HP tissues showing premalignant characteristics. The absence of established surveillance guidelines complicates post-resection monitoring. While malignancies like adenocarcinoma, intraductal papillary mucinous neoplasm, and solid pseudopapillary tumors have been reported, they are extremely rare [7].

Among patients with symptomatic gastric HP, mid-abdominal pain is the most commonly reported symptom, occurring in up to three-quarters of cases. Other symptoms like nausea, heartburn, dyspepsia, diarrhea, weight loss, hematemesis, and melena are less common [5].

Complications associated with gastric HP include acute or chronic pancreatitis, pancreatic necrosis, pseudocyst formation, gastric outlet obstruction, perforation, and rarely, pancreatic carcinoma. Diagnosis is often delayed or missed due to various factors [5]. These include the diverse and nonspecific nature of symptoms, rarity of clinical expression, submucosal or muscularis location hindering detection by standard methods, pleomorphic macroscopic appearance confused with other lesions, absence of typical endoscopic features in a significant percentage of cases, and insufficient enzyme production by inflamed ectopic pancreatic tissue to elevate serum amylase or lipase levels above normal [5,6].

Making a pre-operative diagnosis of HP is highly challenging, although maintaining a high clinical suspicion can aid in the process. On a CT scan, it typically manifests as an endoluminal enhancing lesion. During endoscopic examination, it presents as a round to oval submucosal lesion with central ulceration or umbilication. However, the definitive diagnosis is only achieved through histopathological examination, where pancreatic ducts, acini, and/or islet cells may be observed [5,7].

HP was classified according to Heinrich’s classification. Briefly, HP Type I includes acini, ducts, and endocrine islet cells, Type II contains acini and ducts, but no islet cells, and Type III only contains pancreatic ducts [8]. Based on Heinrich’s classification, this case had been classified as Type 2 with an excision biopsy of the specimen showing pancreatic tissue with lobular architecture, pancreatic acini, and ducts with surrounding fibromuscular tissue showing mild lymphocytic infiltrate without atypia/features of malignancy. A few similar cases reported in scientific medical literature are listed in Tab. 1, based on their clinical findings, investigations, and treatments [9–17]. Surgical removal proves to be a straight--forward and effective treatment, underscoring the importance of distinguishing it from neoplastic causes.

Conclusion

Despite the availability of sophisticated diagnostic tools, the preoperative diagnosis of an ectopic pancreas remains difficult, and the inability to distinguish it from neoplastic lesions frequently necessitates surgical excision. The final diagnosis of HP in our case was made following histopathology excision, despite excellent clinical judgment and technological advancements in diagnostic tools – thus the „diagnostic dilemma“.

In brief, even though ectopic pancreas is an uncommon condition, doctors should treat it as a differential diagnosis for extramucosal gastric lesions because a straightforward excision may be able to treat it.