Primary adenocarcinoma from a gastric heterotopic pancreas: A case report

Abstract

BACKGROUND

Malignant transformation of an ectopic pancreas is exceptionally rare, posing significant diagnostic challenges. As such, there are currently no established management guidelines. We present a rare case of gastric adenocarcinoma arising from ectopic pancreatic tissue and provide a systematic review of previous case reports of adenocarcinomas derived from ectopic pancreas in the stomach, duodenum, and jejunum in the past 20 years. We provide an overview of the clinicopathological characteristics and discuss critical diagnostic and therapeutic considerations.

CASE SUMMARY

A 58-year-old female was admitted to our hospital in August 2024 due to elevated carbohydrate antigen 19-9. Relevant examinations found a huge abdominal tumor that was radiologically adherent to both the pancreatic head and the greater curvature of the gastric antrum. A preoperative endoscopic biopsy-confirmed adenocarcinoma, prompting a pancreaticoduodenectomy. Histopathological examination subsequently identified the tumor as an adenocarcinoma originating from a gastric ectopic pancreas. Adjuvant chemotherapy (gemcitabine + capecitabine) commenced on November 13, 2024. After five cycles, surveillance imaging (April 3, 2025) revealed metastatic progression, prompting a transition to second-line therapy (nab-paclitaxel + gemcitabine). The patient is currently undergoing regular chemotherapy and has been followed up regularly, and the condition has not changed significantly compared with before.

CONCLUSION

We hope that our findings will facilitate the clinical recognition of this entity and help to increase knowledge regarding its management.

Key Words: Heterotopic pancreas; Adenocarcinoma; Endoscopic ultrasound; Endoscopic ultrasound-guided fine needle aspiration; Tumor marker; Treatment; Case report

Core Tip: We have described a case of adenocarcinoma arising from gastric heterotopic pancreas. If the cancer has invaded the mucosal layer, gastric endoscopy with biopsy has great utility for preoperative diagnosis. Alternatively, evaluation can be performed with endoscopic ultrasound, and with endoscopic ultrasound-guided fine needle aspiration if necessary. Tumor markers need to be regularly tested in the postoperative follow-up of such patients. Clinicians need to be mindful of the possibility of malignant transformation of heterotopic pancreas, especially with duodenal or gastric submucosal tumor-like lesions with obstructive symptoms.

INTRODUCTION

Heterotopic pancreas (HP), also known as ectopic or aberrant pancreas, is defined as histologically confirmed pancreatic tissue located outside the normal pancreatic gland that lacks any anatomic, vascular, or neural connection to the orthotopic pancreas. HP was first described in 1727 within an ileal diverticulum[1]. HP may occur anywhere in the gastrointestinal tract, but is most commonly seen in the duodenum (9%-36%), stomach (24%-38%), jejunum (0.5%-27%), and Meckel’s diverticulum (2%-6.5%)[1]. Based on Heinrich’s original histological classification system, HP can be categorized into three distinct subtypes: Types I-III. However, Fuentes and others have since modified this system to include a fourth subtype, type IV[2].

HP is relatively uncommon and typically asymptomatic. Its malignant transformation is exceptionally rare, with reported incidence rates of 0.7%-1.8% among all HP cases[1]. Morphologically, malignant HP lesions may present as smooth nodules or, less frequently, irregular masses. Combined with the tissue’s ectopic nature, this poses significant diagnostic challenges. Although conventional endoscopic biopsy can identify the adenocarcinoma, it often fails to detect its ectopic pancreatic origin. Given the diagnostic complexity and the scarcity of reported cases, we have supplemented our presentation of this rare instance of gastric adenocarcinoma arising from HP with a comprehensive literature review (Table 1). We aim to facilitate the clinical recognition of this pathology and to consolidate existing knowledge regarding its diagnosis and therapeutic management.

Table 1 Clinicopathological characteristics of heterotopic pancreatic adenocarcinomas (n = 21).

Ref.	Sex, age	Location	Morphology	Clinical presentation	Tumor markers	Diagnostic methods	Histology	Heinrich type	Initial diagnosis	Outcome	Adjuvant therapy
Matsuki et al[5], 2005	Female, 58 years old	Gastric antrum	SET with stenosis	Gastric outlet obstruction (vomiting)	CEA, CA19-9: Normal	EUS: Diffuse wall thickening in prepyloric region	Adenocarcinoma	II	Suspected malignancy	No recurrence (1.5 years)	None
Fujita et al[13], 2008	Female, 64 years old	Jejunum	Umbilicated mass	Abdominal distension/epigastric pain	Not tested	DBE: Umbilicated mass (intraoperative confirmation)	Adenocarcinoma	I	Jejunal cancer	Death (5 months after surgery; metastasis)	Gemcitabine
Bini et al[14], 2010	Male, 56 years old	Duodenum (D1)	SET	Vomiting	CA19-9/CA125/AFP: Normal limits	EGD + EUS: Submucosal hypoechoic lesion and biopsies were performed	Adenocarcinoma	I	Adenocarcinoma of unknown origin	Not reported	Referred for chemotherapy
Song et al[15], 2012	Male, 74 years old	Jejunum	Perforating tumor	Acute abdominal pain, stool problems	CA19-9 elevated	Not performed	Adenocarcinoma	II	Peritonitis from perforation of sigmoid colon cancer	Not reported	Not reported
Stock et al[16], 2011	Female, 79 years old	Duodenum (D4)	Not described	Early satiety (2 years)	Not tested	EGD: Duodenal mass	Adenocarcinoma	I	Not reported	Not reported	Adjuvant chemotherapy
Fukumori et al[9], 2011	Female, 76 years old	Gastric pylorus	SET	Not reported	CA19-9: 177.5 to 279.5 U/mL	EUS: SMT	Adenocarcinoma	II	GIST	Not reported	Not reported
Okamoto et al[17], 2012	Female, 75 years old	Stomach	SET	Epigastric pain	CEA, CA19-9 elevated	EGD: Subepithelial tumor	Adenocarcinoma	I	SET	No recurrence (11 years)	Not reported
Kinoshita et al[18], 2012	Female, 62 years old	Duodenum	Stenotic	Vomiting/epigastric pain	CEA, CA19-9 elevated	EGD: Gastric outlet obstruction	Adenocarcinoma	I	Advanced gastric cancer	No recurrence (12 months)	Not reported
Ginori et al[19], 2013	Male, 86 years old	Duodenal bulb	Stenotic	Abdominal pain/dyspepsia for 2 months	Not tested	Not performed	Adenocarcinoma	I	Acute cholecystitis	Gastrectomy, alive with metastasis	Not reported
Endo et al[4], 2014	Male, 75 years old	Duodenum	Stenotic	Epigastric pain/tarry stools	CEA, CA19-9 increased	EUS-FNA: SMT	Adenocarcinoma	I	Duodenal cancer	No recurrence (5 years)	Not reported
Endo et al[4], 2014	Male, 73 years old	Stomach	SET	Epigastric pain	CEA, CA19-9: Normal	EUS: 4th layer hypoechoic mass (EMR-C + biopsy)	Adenocarcinoma	I	Gastric cancer	Lymph node metastasis (2 years follow-up)	Not reported
Fukino et al[12], 2015	Male, 62 years old	Duodenum (D3)	SET	6 kg weight loss in (4 months)	CEA: Normal limits, CA19-9/DUPAN-2/SPan-1 elevated	Duodenal fibroscopy: SMT	Adenocarcinoma	IV	Duodenal carcinoma	Death (33 months after surgery)	S-1 + cisplatin to radiation + GEM (recurrence)
Mehra et al[10], 2015	Male, 51 years old	Duodenum (D3)	Not described	Abdominal pain/nausea	Not tested	EGD: Mucosal growth in duodenum	Adenocarcinoma	II	Not reported	No recurrence	Not reported
Hisanaga et al[20], 2020	Female, 70 years old	Duodenum	Rough, protuberant lesion	Incidental (diabetes)	Not tested	EUS: Multilocular protuberant lesion	Adenocarcinoma	I	Pancreatic carcinoma	No recurrence (10 months)	Not reported
Jung et al[21], 2020	Male, 75 years old	Stomach	Submucosal lesion with gastric outlet obstruction	Dyspepsia, nausea/3 kg weight loss within 1 month	CEA, CA19-9 increased	GIE and EUS (2008) hypoechoic lesion involving the 2nd/3rd layers; GIE (2018) tumor increased	Adenocarcinoma	Not specified	Gastric outlet obstruction	Follow-up < 6 months	Capecitabine + oxaliplatin
Oto et al[22], 2021	Male, 37 years old	Stomach	Pylorus stenosis	Nausea/upper abdominal pain	Not tested	EGD: Pyloric stenosis	Adenocarcinoma	Not specified	Not reported	Not reported	Not reported
Hirokawa et al[11], 2021	Female, 65 years old	Duodenum (D1)	Ulcer formation	Epigastric discomfort	CEA, CA125 elevated	EGD: Ulcerated tumor (biopsy-confirmed)	Adenocarcinoma	Not specified	Unresectable duodenal cancer	Progression (24 months)	Trastuzumab (HER2+) pre-operation + chemo, post-operation
Qian et al[2], 2023	Female, 59 years old	Stomach	Stenotic	Abdominal discomfort/acid regurgitation	Not tested	EGD: Pyloric area congestion and swelling; pyloric canal stenosis	Adenocarcinoma	III	Pyloric obstruction and adenocarcinoma	Recurrence and metastasis (1-year post-op)	Gemcitabine + tigecycline
Woo et al[6], 2023	Male, 65 years old	Duodenal bulb	Stricture	Dyspepsia/vomiting	Not tested	EGD: Duodenal stricture	Adenocarcinoma	III	Benign stricture	No recurrence (24 months)	FOLFIRINOX
Yamaoka et al[8], 2015	Female, 65 years old	Jejunum	SET	Incidental finding	CA19-9: 635 U/mL, CEA: 22 ng/mL	DBE: SMT	Adenocarcinoma	II	Peritoneal metastasis from colon cancer	Peritoneal recurrence (9 months)	S-1 to gemcitabine + nab-paclitaxel
Ji et al[7], 2024	Female, 75 years old	Stomach (antrum)	SMT	Health screening	CA19-9 elevated	EGD: Submucosal bulge	Adenocarcinoma	Not specified	Primary pyloric malignancy	Not reported	Not reported

Adopted from Cazacu et al[1]. SET: Subepithelial tumor; CEA: Carcinoembryonic antigen; CA19-9: Carbohydrate antigen 19-9; EUS: Endoscopic ultrasound; DBE: Double-balloon enteroscopy; D1/D3/D4: Duodenal 1^st/3^rd/4^th portion; CA125: Carbohydrate antigen 125; AFP: Alpha-fetoprotein; EGD: Esophagogastroduodenoscopy; GIST: Gastrointestinal stromal tumor; EUS-FNA: Endoscopic ultrasound-guided fine needle aspiration; EMR-C: Endoscopic mucosal resection with cap; GEM: Gemcitabine; HER2+: Human epidermal growth factor receptor 2-positive; S-1: Tegafur/gimeracil/oteracil; SMT: Submucosal tumor; GIE: Gastrointestinal endoscopy.

CASE PRESENTATION

Chief complaints

A 58-year-old woman presented to our institution in August 2024 after routine blood tests revealed an elevated carbohydrate antigen 19-9 (CA19-9) level (93 U/mL; normal range 0-37 U/mL). Although this can be indicative of other conditions, high CA19-9 is sufficiently associated with pancreatic cancer to suggest the need for further investigation. The patient’s physical examination and vital signs were unremarkable.

History of present illness

An elevated CA19-9 level.

History of past illness

No other medical conditions.

Personal and family history

The patient reported no significant personal or family medical history.

Physical examination

No relevant factors were identified on physical examination.

Laboratory examinations

Routine blood tests revealed an elevated CA19-9 level (93 U/mL; normal range: 0-37 U/mL).

Imaging examinations

Contrast-enhanced abdominal computed tomography (CT) identified a cystic lesion in the right upper abdomen (Figure 1). This showed close anatomical relationships with both the pancreatic head and the greater curvature of the gastric antrum. An initial radiological assessment favored a benign pathology, with differential diagnoses including intestinal duplication and pancreatic cystadenoma. The subsequent pancreatic protocol magnetic resonance imaging with diffusion-weighted imaging (Figure 2) confirmed these findings but showed no evidence of malignancy.

Figure 1 Abdominal computed tomography findings in a 58-year-old woman with elevated carbohydrate antigen 19-9. A: The non-contrast-enhanced coronal view demonstrated a 7.1 cm × 4.8 cm hypodense cystic lesion (orange arrow) in the right upper quadrant; B and C: An arterial-phase contrast-enhanced coronal image reveals the lesion’s (orange arrow) intimate anatomical relationship with both the pancreatic head (P in B) and the greater curvature of the gastric antrum (G in C). The absence of a septum was found, and no significant arterial enhancement or suspicious nodularity of the cyst wall was found.

Figure 2 Contrast-enhanced magnetic resonance imaging findings in a 58-year-old woman with elevated carbohydrate antigen 19-9. Magnetic resonance imaging revealed a well-circumscribed, oval cystic lesion (62 mm × 38 mm, SE3 IM9) in the right upper abdomen, with prolonged T2 signal intensity. The lesion was closely adjacent to the pancreatic head and the gastric antrum, with no fat plane separation. Peripheral wall enhancement was observed postcontrast.

An upper endoscopy revealed the following: (1) A large, soft submucosal lesion involving the pylorus and greater curvature of the gastric antrum, with preserved luminal patency; (2) An ulcerated lesion at the duodenal bulb-descending junction, with luminal narrowing and raised margins (Figure 3); and (3) Endoscopic ultrasonography (EUS) identified a 7 cm × 4.8 cm mixed cystic-solid mass with clear demarcation from the adjacent organs but a loss of interface with the fourth layer of the gastric wall (Figure 4).

Figure 3 Endoscopic findings of ectopic pancreatic carcinoma in a 58-year-old woman. A: A submucosal lesion with central umbilication was observed at the greater curvature of the gastric antrum, accompanied by extrinsic compression near the pylorus (soft on probing, with pyloric patency preserved); B and C: A giant ulcer with raised margins and a white fibrinoid base was found at the duodenal bulb-descending junction, causing significant luminal stenosis; D: The stenosis was nearly obstructive, the tumor in the descending duodenum exhibited mucosal breach and a coarse, irregular surface.

Figure 4 Endosonographic features of an abdominal solid cystic mass in a 58-year-old woman. A: A multilobulated solid cystic mass (7.0 cm × 4.8 cm) was identified; B: The mass extended to the duodenal bulb-descending junction, causing luminal stenosis. The duodenal wall showed tumor infiltration (irregular hypoechoic thickening of up to 1 cm). The cyst wall exhibited hypoechoic unevenness, suggesting mural involvement; C: The lesion had ill-defined borders with the fourth layer of the gastric wall (as indicated by green arrow).

FINAL DIAGNOSIS

Biopsy of the ulcer confirmed moderately differentiated adenocarcinoma, obviating the need for the planned endoscopic ultrasound-guided fine needle aspiration (EUS-FNA). Notably, the patient’s CA19-9 level decreased to 43 U/mL preoperatively. The patient underwent pancreaticoduodenectomy with regional lymphadenectomy. Pathological examination of the specimen (Figure 5) demonstrated the following: (1) Cystic-predominant, moderately differentiated adenocarcinoma; (2) Tumor centered in the gastric antral wall with invasion of the pylorus/duodenum; and (3) Transmural invasion through the mucosal layers into the subserosa. This led to a final diagnosis of malignant transformation of a gastroduodenal ectopic pancreas (pT3N2M0, stage III).

Figure 5 Histopathological analysis of a resected specimen from a 58-year-old woman with a gastric mass. A-F: Histopathology confirmed a nonpancreatic primary adenocarcinoma with predominant gastric involvement. The lesion exhibited cystic degeneration and extended to the pyloroduodenal region, forming mucosal ulcers. Representative section demonstrating the lesion’s architecture, including the serosal layer (yellow arrow) and the muscularis propria (orange arrow) (A). Infiltrative irregular glands (yellow dashed box) exhibiting malignant cytological features (nuclear pleomorphism and a crowded growth pattern) were observed within the muscularis propria (B and E). Tumor invasion through the mucosal to subserosal layers (orange arrow) of the gastrointestinal wall was apparent, with multiple tumorous cells and glands in the muscularis propria (yellow dashed box) (C). Cystic dilation (green arrow) of the ectopic pancreatic ductal structures (D). A high-power view revealed glandular epithelial cells with abundant eosinophilic cytoplasm and elongated nuclei, consistent with pancreatobiliary adenocarcinoma (F).

TREATMENT

Adjuvant chemotherapy (gemcitabine + capecitabine) commenced on November 13, 2024.

OUTCOME AND FOLLOW-UP

After five cycles, surveillance imaging (April 3, 2025) revealed metastatic progression, prompting a transition to second-line therapy (nab-paclitaxel + gemcitabine). The patient’s CA19-9 level had normalized by December 23, 2024, and remained within normal limits at her most recent follow-up.

DISCUSSION

Our case reported here is from the stomach and also has a close relationship with the first portion of the duodenum. Although pancreatic heterotopia can occur throughout the entire gastrointestinal tract, the most frequent sites are the stomach (25%-60%), duodenum (30%), and jejunum (15%)[3]. When it occurs in the stomach, the ectopic pancreas is usually located within a few centimeters of the gastroduodenal junction[3]. This form is often symptomatic, with patients complaining of dyspepsia, nausea, upper gastric pain, acid reflux, abdominal distension, early satiety, vomiting, and weight loss. HP rarely causes abnormal stools directly, but they may result indirectly through mechanical effects or local inflammation. If the patient has intractable diarrhea or related manifestations, clinicians should look first for other diseases of the digestive system. Only 16.7% (4/22 cases, including our patient) of the patients identified in our review were asymptomatic, and the lesions were found incidentally. This suggests that when malignant transformation of HP occurs, patients are more prone to clinical symptoms or their original symptoms worsen.

Among the reviewed cases, we found that the morphology of adenocarcinomas arising from HP varies considerably. Preoperative diagnosis of a malignant ectopic pancreas with stenotic or submucosal tumor (SMT) morphology and no ulceration can be difficult using imaging studies such as CT and radiography. This is because imaging can only indicate the presence of a mass; it cannot determine its nature. For this reason, most of the reviewed cases of adenocarcinomas arising from an ectopic pancreas were resected as SMTs with tentative diagnoses of gastrointestinal stromal tumor, lymphoma, or other[4]. The mass in our patient had a predominantly SMT-like appearance, with focal ulceration in the duodenum. Malignant transformation of an HP usually occurs intramurally, and involvement of the overlying mucosa occurs late in the course of the disease. While upper endoscopy with conventional biopsy at the location of the tumor rupture can obtain pathological findings, it often fails in SMT-like lesions. The utility of EUS-FNA and endoscopic mucosal resection with cap for histological diagnosis has been demonstrated for many gastrointestinal and pancreatic malignancies. EUS is especially helpful in the diagnosis of SMTs. EUS-FNA combined with immunohistochemistry can achieve a higher histological diagnostic rate. An endoscopic mucosal resection with cap is an endoscopic mucosal resection performed using a panendoscope with a fitted transparent plastic cap. This, followed by a biopsy[4], should be considered before selecting a treatment approach. Matsuki et al[5] have reported a case with no distinct cystic lesion on EUS due to its obscuration by severe stenosis. Therefore, although EUS is generally helpful for the diagnosis of SMTs, the location of the tumor may determine the clarity of the scan. The detection of cystic components inside the tumor is helpful for the diagnosis of HP[5].

Most patients with malignant HP have clinical symptoms. It has been reported that the size of non-neoplastic epithelial tissue is usually < 4 cm, whereas malignant HP is more often > 4 cm[2]. In our case, the mass was about 7 cm × 4.8 cm, which was sufficiently large to suggest a high-risk lesion. Woo et al[6] analyzed 15 cases and reported a size range of malignant duodenal HP of 12-55 mm, with a mean of 29.6 mm. Accordingly, they recommend early treatment of HP to prevent malignant transformation, especially when the lesion is > 1 cm or associated with clinical symptoms of obstruction or weight loss. According to Heinrich’s classification with Fuentes’ modification, HP can be of four types (described above in the classification and demographics subsection of the literature review). In the cases we reviewed, Heinrich types I and II were most common (63.6%)[2]. As the reviewed cases were all malignant, we could not draw a clear conclusion about differences in the probability of malignant transformation between Heinrich types. It was also unclear whether these types were relevant to prognosis and survival. To facilitate the collection of sufficient data to address such questions, a multicenter database needs to be established. The most frequent histological malignancy subtype arising from HP was adenocarcinoma. Other malignancies included anaplastic carcinoma, mucinous cystadenocarcinoma, acinar cell carcinoma, solid pseudopapillary tumor, pancreatoblastoma, perivascular epithelioid cell tumor, and neuroendocrine tumor[7]. Previous studies have found type I HP to be the most common source of malignant tumors. Our review confirmed that type I accounts for the largest proportion of all HP. The biological behavior of type I HP appears to most closely mimic that of a normal pancreas because it contains acinar and islet cells; however, all subtypes have the potential for malignancy, including ductal adenocarcinomas, acinar cell carcinomas, and neuroendocrine tumors. Types II and III are primarily ductal, with similar molecular characteristics to pancreatic ductal adenocarcinoma, such as KRAS and TP53 mutations. Future research investigating the differences in the frequency of driver gene mutations between the Heinrich subtypes is warranted. The interstitial components of HP such as inflammation and fibrosis may affect their malignant transformation owing to differences in their anatomical location (stomach, duodenum, or jejunum) and type. For example, chronic inflammation of an ectopic pancreas in the stomach (mostly type I/II) could be more or less likely to promote malignancy. Whether the immune microenvironment (e.g., T cell infiltration and programmed death-ligand 1 expression) in a malignant ectopic pancreas is affected by the primary site (e.g., stomach vs small intestine) also requires further investigation. We speculate that Heinrich type may indirectly regulate cancer risk and the HP subtypes due through differences in the histological structure, microenvironment, and molecular characteristics. Future research should use multi-omics to analyze pathological cohorts, focusing on exploration of commonalities between the mechanisms of the ductal components of type II/III HP and pancreatic ductal adenocarcinoma.

In our patient, the initial serum CA19-9 level was significantly elevated but decreased to a normal level soon after surgery. Ji et al[7] suggest that elevated serum CA19-9 may be diagnostically helpful, as approximately 57% of patients with HP adenocarcinoma have an increased CA19-9. Woo et al[6] found that 50% of the cases they identified had increased CA19-9 or carcinoembryonic antigen (CEA) levels. In our review, other tumor markers such as DUPAN-2, SPan-1, and CA125 were also found to be increased in some of the cases. In a case reported by Yamaoka et al[8] in 2015, the tumor markers CA19-9 and CEA increased considerably after a colectomy as a result of adenocarcinoma arising from HP in the small intestine. The patient underwent a laparoscopic jejunectomy with regional lymph node dissection. One month after surgery, her CA19-9 level had decreased to a normal level. However, 9 months after surgery, her serum CA19-9 and CEA levels had increased again, and peritoneal metastasis from HP adenocarcinoma was suspected. A case of gastric HP was reported by Fukumori et al[9] in 2011. Initially, a neoplastic lesion was detected in the pyloric region of an upper esophagogastroduodenoscopy of a 76-year-old woman. The lesion required biopsy, but because it was classified as Heinrich type I, it was only observed temporarily. Following blood tests 2 years later found that the patient’s CA19-9 had increased from 177.5 to 279.5. Esophagogastroduodenoscopy, EUS, and a CT scan were performed, and, as the results could not rule out malignancy, the patient underwent gastrectomy on the pylorus side and lymph node dissection. This led to the eventual diagnosis of HP cancer. Thus, tumor markers, especially CA19-9 and CEA, appear to be useful indices of potential HP malignancy and its subsequent metastasis. Therefore, tumor markers should be tested regularly in HP patients and in the postoperative follow-up of such patients. If elevated tumor markers are found in a patient with a history of HP, the possibility of malignant transformation needs to be considered. However, a previous report found the rate of tumor-positive markers, including CA19-9 and CEA, to be lower in patients with HP adenocarcinoma than those with primary pancreatic cancer[4].

Gastric HP is usually asymptomatic and requires no treatment. In high-risk cases, a resection is required, with histological confirmation of non-malignancy. High-risk is indicated by an increasing size and symptoms such as ulceration, bleeding, and pyloric obstruction. A previous study reported surgical resection as the diagnostic approach for malignant ectopic pancreas in 87% of the 54 included cases[1]. In our case, the patient was treated with gemcitabine + capecitabine as adjuvant chemotherapy, but metastatic progression was found at the 6-month follow-up. Because of the small number of reports of adenocarcinoma arising from HP, there is no clear evidence of the efficacy of chemotherapy or the optimal type of adjuvant therapy[6]. The patient described by Mehra et al[10] responded well to gemcitabine + oxaliplatin adjuvant therapy; however, the general prognosis for HP adenocarcinoma is not well known. Further detailed studies may be able to clarify this. In Hirokawa’s case[11], trastuzumab treatment was effective against human epidermal growth factor receptor 2-positive adenocarcinoma originating from HP tissue in the duodenum. It can be seen that targeted therapy has shown potential in the treatment of ectopic pancreatic cancer, and routine detection of molecular markers (such as human epidermal growth factor receptor 2/BRAC) is necessary. In a case reported by Fukino et al[12], gemcitabine was effective for recurrent adenocarcinoma arising from a duodenal ectopic pancreas. At present, immunotherapy for pancreatic cancer has progressed from being almost entirely ineffective to a stage of limited breakthrough. Individualized vaccines and microtargeting strategies are the most promising directions for future research. Therefore, we look forward to corresponding increases in the effectiveness of immunotherapy for ectopic pancreatic cancer. We believe that there will be more breakthroughs in the drug treatment of ectopic pancreatic cancer in the future.

The recurrence rate of HP cancer is low. A few patients have remained alive without recurrence more than 5 years after resection of adenocarcinoma arising from ectopic gastric or duodenal pancreas, which has a 5-year survival rate of 10%. Reports suggest a more favorable prognosis than for ordinary pancreatic cancer because of the earlier presentation of gastrointestinal obstruction and other symptoms, allowing more expeditious control of the disease[8].

CONCLUSION

We have described a case of adenocarcinoma arising from gastric HP. Although the incidence of gastric adenocarcinoma arising from HP is rare, a careful diagnostic and therapeutic approach should be adopted in suspected cases. If the cancer has invaded the mucosal layer, gastric endoscopy with biopsy has great utility for preoperative diagnosis. Alternatively, evaluation can be performed with EUS, and with EUS-FNA if necessary. Tumor markers need to be regularly tested in the postoperative follow-up of such patients. Until now, there has been no clear evidence for the efficacy of chemotherapy or the optimal type of adjuvant therapy. However, this case found that gemcitabine + capecitabine and gemcitabine + oxaliplatin have proven to be effective in several reports. Despite their rarity, clinicians need to be mindful of the possibility of malignant transformation of HP, especially with duodenal or gastric SMT-like lesions with obstructive symptoms.