Gastrointestinal Tract Heterotopic Pancreas: Asymptomatic Pathology?

Congenital anomalies involving the pancreas can be categorized into fusion anomalies, duplication anomalies and migration anomalies, with heterotopic pancreas belonging to the latter [1]. Heterotopic pancreas, firstly described by Jean Schultz in 1727 and histopathologically confirmed by Klob in 1859 [2], is also known as ectopic, aberrant or accessory pancreas, as well as pancreatic rest, choristoma and adenomyoma [3]. It is defined as the presence of pancreatic tissue away from the usual anatomical location of the pancreas, without vascular or ductal continuity. This anatomical anomaly is similar to the original pancreas in terms of genetic make-up and physiological function. Several theories regarding the pathogenesis of heterotopic pancreas were suggested, with the “misplacement” theory being the most accepted one. According to the aforementioned theory, pancreatic tissue deposits are dropped away from the main pancreas, into the developing gastrointestinal tract [4]. Although the incidence rate of said anomaly is considered low, the precise rate is unknown, with autopsy results demonstrating a prevalence rate of 0.5-13.7% [5]. Heterotopic pancreas can also be found incidentally following stomach resection and other upper gastrointestinal surgeries in 0.9% and 0.2%, respectively [6, 7]. It is more common in males than in females with a male to female ratio of 3:1, most often discovered during the fifth to sixth decades of life [8]. Heterotopic pancreas can be found at any level of the gastrointestinal tract, with more than 90% of cases diagnosed in the stomach, duodenum and proximal jejunum [9]. The duodenum, mostly the descending part, is the most frequent site of involvement (27.7%), followed by the stomach (greater curve) and proximal jejunum (usually at the Treitz ligament level) in 25.5% and 15.9%, respectively [4, 7, 10]. Other less common reported gastrointestinal tract sites include ileum (2.8%), Meckel’s diverticulum (5.3%), colon, esophagus, omentum, spleen, liver and the mesentery. only few cases, published in the English literature as case reports, discuss heterotopic pancreas at the esophagus, mainly the distal part [11]. Moreover, up to 11 cases of mesenteric heterotopic pancreas were reported. Some extremely rare locations of heterotopic pancreas reported include lungs, mediastinum and the gallbladder [12]. So far, less than 40 cases of gallbladder heterotopic pancreas have been reported worldwide. Due to the fact that only a few case reports of heterotopic pancreas at the gallbladder have been reported, the clinical presentation and radiological findings are ill defined. Grossly, heterotopic pancreas along the gastrointestinal tract is firm subepithelial lesions, lobular in shape with well defined interface with the nearby structures [13]. Histologically, heterotopic pancreas is a true pancreatic gland that includes the same components as for the native pancreas, and categorized into three types according to its component [14]: type I (all types of pancreatic tissue), type II (only pancreatic ducts) and type III (only pancreatic acini). Due to the previously mentioned fact, any pathology affects the native pancreas, such as inflammation or neoplastic transformation, can develop as well in the heterotopic counterpart. The risk for malignant transformation is extremely rare, and can arise from either exocrine or ductal components. Reviewing the current English literature reveals very limited number of studies, mainly small volume retrospective and case series studies, limited to single center experience regarding heterotopic pancreas. The majority of the data about this unique anomaly is published as case reports. Although regarded in English literature as an incidental radiological/operative finding, clinical presentation of heterotopic pancreas differs from one study to the other, and depends on several parameters such as patients’ age, gastrointestinal tract location, lesion size, timing of surgery and mucosal involvement. In their large series studies, Zhang et al [15] and Betzler et al [16] reported that almost 85% of heterotopic pancreas cases were diagnosed incidentally. On the other hand, heterotopic pancreas was symptomatic in 35% and 100% of patients in other studies [17-19], respectively. The most common presenting symptom in the previously mentioned studies was abdominal pain (23-50%). Other reported symptoms were nausea and vomiting (27%), weight loss (18%) and upper gastrointestinal hemorrhage (13%). Patients’ age as a parameter for symptoms was reported by Persano et al [20]. In his study, which included 14 pediatric Manuscript submitted January 17, 2021, accepted February 4, 2021 Published online February 19, 2021