A Rare Adenocarcinoma of Ectopic Pancreatic from Duodenum: A Case Report (2023)

Background

Ectopic pancreas, also known as abnormal pancreas, was firstobserved in 1727 in an ileal diverticulum [1]. Ectopic pancreasis a condition in which pancreatic tissue appears outside of theoriginal pancreas and has no vascular or nerve connection topancreas [2]. Ectopic pancreas is most commonly found in thegastrointestinal tract, but it can also be found in the biliary tract,liver, lung, brain, and other areas [3-7]. Malignant transformationof an ectopic pancreas is uncommon. According to a study, from2000 to 2020, only 12 cases of ectopic pancreatic malignancy ofduodenum were reported in Pubmed [8]. We present a case ofectopic pancreatic cancer that originated in the first portion ofthe duodenum.

Case introduction

A 68-year-old male presented to our hospital with epigastricpain and weight loss for three months. PET-CT in the other hospital indicated a large abdominal mass involving the gastric antrum and duodenum, which was considered to be gastrointestinalstromal tumor with right superior phrenic, portal vein and retroperitoneal lymph node metastasis. Following admission, relevantexaminations were performed, and the patient’s serum CA19-9were 153.2 IU/L and CA125 were 101.3 IU/L. Combined with upper abdominal MRI (Figure 1 A,B) and gastroscopy (Figure 1 C,D),the possibility of gastrointestinal stromal tumor was still considered to be high. With the consent of the family, the operationwas performed.During the operation, it was discovered that thetumor originated from the first portion of the duodenum and wasclearly not associated with the pancreas. Then, a distal gastrectomy was performed along with regional lymph node dissection.Pathological findings revealed that it was a moderately differentiated ductal adenocarcinoma infiltrating the muscular layer of theduodenum, with vascular invasion and lymph node metastasis ofthe duodenal ligament, but no nerve invasion (Figure 2). Following surgery, the patient underwent two courses of gemcitabinechemotherapy and then refused further treatment. Six months after surgery, abdominal CT (Figure 3) revealed no signs of tumor recurrence, and serum CA19-9 and CA125 levels remained normal.

Discussion

Patients with ectopic pancreas usually have no specific symptoms, though a few may experience non-specific symptoms suchas abdominal pain, dyspepsia, or digestive tract obstruction dueto inflammation and tumor [9]. Ectopic pancreas is typically foundin the submucosa, making imaging and general endoscopy difficult to diagnose. Although endoscopic ultrasound can help indiagnosis, a definitive diagnosis still requires a fine-needle aspiration biopsy or post-operative pathological biopsy [6].

The risk of malignant transformation of ectopic pancreas isvery low, estimated to be between 0.7% and 1.8% in the literature[10,11]. About one-third of all cases of ectopic pancreatic canceroccur in the stomach, followed by the duodenum and jejunum,with cases also occurring in the esophagus, spleen, rectum, mesentery, liver, Meckel diverticulum, and brain [6]. Because of the disease's different location, ectopic pancreatic cancer can causea variety of nonspecific clinical symptoms, the most common ofwhich are gastrointestinal and systemic manifestations, such asabdominal pain, nausea, dyspepsia, and weight loss, and a fewpatients may experience abnormal defecation, gastrointestinalbleeding, hypoglycemia, and so on [9]. About half of the patientshad elevated tumor markers, with the most common being an increase in serum CA 19-9, but the positive rate of tumor markerswere lower than pancreatic cancer [12]. In our case, the patientexperienced abdominal pain, weight loss, and gastrointestinal bleeding, as well as an increase in the serum CA 19-9 and CA 125.However, these differences are insufficient to differentiate it fromgastrointestinal stromal tumor, gastrointestinal neuroendocrinetumor, gastric carcinoid, gastric lymphoma, and gastric cancer.Imaging, such as abdominal CT and MRI, can only pinpoint thelocation of the tumor and cannot provide a definitive diagnosis.Endoscopy has the function of differential diagnosis, but tissuebiopsy, even if performed, is not diagnostic because the sampling location is usually superficial. Endoscopic ultrasonographyis considered to be an effective method for the diagnosis of ectopic pancreas. Submucosal lesions can be cytologically evaluatedwhen combined with fine needle aspiration biopsy, making thediagnosis of ectopic pancreatic malignant transformation morereliable [5]. The EUS-FNA was not performed in our case becausethe patient's abdominal pain was severe and required curative orpalliative surgery. Pathological diagnosis of surgical resection istypically used as the gold standard for ectopic pancreatic cancerdiagnosis. Some researchers proposed diagnostic criteria for ectopic pancreatic cancer as early as 1974 [9]: (1) The tumor must bein or near the ectopic pancreas; (2) the transition zone betweenpancreatic structure and cancer shall be observed, while metastatic tumor or adjacent malignant tumor infiltration ought to beexcluded; and (3) non-neoplastic ectopic pancreatic tissue wassupposed to include well-developed acini and ductal structures.

Because of its rarity, treatment for ectopic pancreatic canceris limited. Surgical resection is usually the first option, and different surgical methods, such as pancreaticoduodenectomy, distalgastrectomy, pylorus-preserving pancreaticoduodenectomy, andsubtotal stomach-preserving pancreaticoduodenectomy, can bechosen depending on the specific location of the tumor [13-15].If the intraoperative frozen pathological examination reveals thatthe tumor is malignant, regional lymph node dissection should beperformed routinely. There is currently no evidence that chemotherapy is effective in the treatment of ectopic pancreatic cancer[6,15]. According to studies, the overall survival time of ectopicpancreatic cancer after surgery is longer than that of pancreaticcancer, and approximately 39% of patients have a survival time ofmore than one year after operation, with a low probability of recurrence after surgical resection, which may be related to the factthat ectopic pancreatic cancer manifests clinical symptoms earlierthan pancreatic cancer [16].

Ectopic pancreas is becoming increasingly common as endoscopic detection and ultrasonic endoscopic technology becomemore widely available. Although the likelihood of malignant transformation of an ectopic pancreas is low, the possibility of malignant transformation should not be overlooked. Specialists shouldhave an understanding of the common sites, clinical characteristics, histological and pathological features, as well as diagnosisand treatment methods for ectopic pancreatic cancer.

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