Discussion
EPT is a rare entity; however, its actual incidence in the gallbladder
is unidentified, as a lack of clinical symptoms can complicate the
diagnosis (5). It can occur anywhere, but the most common locations are
the stomach (27.5%), duodenum (25.5%), colon (15.9%), jejunum, and
spleen (6). By contrast, the presence of EPT in the gallbladder, lung
mediastinum, liver, mesentery, and ileum is considered extraordinary (2,
7). EPT can be diagnosed in any age group, but most cases are between
40-60 years old. Albeit the male-to-female ratio of any other type of
EPT is 3:1, there is a female predominance, specifically for EPT in the
gallbladder, which may be due to the fact that cholecystitis-related
cholecystectomies are more prevalent in women (2, 8). The etiologies of
EPT are still unclear, but three hypotheses about its origin have been
proposed. The first theory, which is widely accepted, suggests that EPT
separates from the primitive pancreas gland during the rotation of the
gastrointestinal tract in the embryogenic period. The second theory
suggests that the longitudinal growth of the intestine from the lateral
budding of the rudimentary pancreas tissue while penetrating the
intestinal wall causes the irregular transportation of the pancreatic
tissue (9, 10). The third theory supports that abnormalities in the
notch signaling system can result in changes in different foregut
endoderm tissue during embryogenesis (11). Jean Schultz first described
the heterotropic pancreas in the 18th century; however, the first
classification was made by Von Heinrich et al. in 1909, which was later
modified by Fuentes in 1973 that consisted of four types (12):
- Type one : acini with ducts and islet-like pancreatic gland
(normal pancreatic tissue)
- Type two : canalicular variant pancreatic duct
- Type three : exocrine pancreas with acinar tissue
- Type four : endocrine pancreas with cellular islets
According to what is mentioned above, this case is compatible with type
three (figure1-3).
These ectopic pieces of tissue macroscopically can appear as an
exophytic mass, similar to polypoid lesions, or as a nodule with a
yellow-colored appearance with sizes varying from a few millimeters to
even 4cm (13). Still, they are generally asymptomatic and only
discovered histopathologically. However, in some cases, it can cause
various nonspecific symptoms, depending on the location. Symptoms can
include jaundice if obstructing bile ducts or biliary colic-like
symptoms (e.g., right upper quadrant pain, anorexia, nausea, and
vomiting after meals); nevertheless, such symptoms presumably result
from simultaneous lithiasic cholecystitis. Other conditions can be
derived from EPT, such as cholelithiasis, acute or chronic
cholecystitis, or carcinoma (2, 10).
As Sato et al. reported that pancreatic enzymes (amylase and lipase)
secreted from EPT in the gallbladder could impact its mucosa leading to
gallbladder dysplasia and carcinoma. Therefore, cases with EPT in the
gallbladder must undergo cholecystectomy as a definite treatment
preventing any potential malignant transformation. Moreover, EPT can
potentially cause the same pathologies as typical pancreatic tissue,
which includes cysts, pseudocysts formation, abscess, and acute or
chronic pancreatitis (14, 15).
Diagnosing EPT in the gallbladder before and during an operation is
impossible. Preoperative radiologic evaluation (ultrasound or computed
tomography scan) usually cannot detect EPT in the gallbladder; neither
this case did (16). Therefore, only a precise histopathologic
examination can provide a definite diagnosis; consequently, it’s
essential for anatomical pathologists to be aware of this uncommon
presentation of EPT in gallbladder to discriminate it from a
masquerading malignancy.