A primary pure pancreatic-type acinar cell carcinoma of the stomach: a case report
© The Author(s). 2017
Received: 22 October 2016
Accepted: 13 January 2017
Published: 19 January 2017
Acinar cell carcinoma represents only 1–2% of exocrine pancreatic neoplasms. On exceptionally rare occasions, primary acinar cell carcinoma can occur in ectopic locations. Herein, we report a case of pure pancreatic-type acinar cell carcinoma arising in the stomach.
A 54-year-old male presented with a gastric submucosal mass detected by endoscopic examination. Laparoscopic wedge resection was performed. Macroscopically, the 2.7 cm yellowish mass was located in the submucosa of the stomach. Microscopically, the tumor was well circumscribed and had a homogeneous acinar architecture. The tumor cells were small and had a minimal amount of cytoplasm. The nuclei of the tumor cells were round to oval with finely dispersed chromatin. The tumor cells were strongly positive for α1-antitrypsin, chymotrypsin, and α1-antichymotrypsin immunostaining, consistent with pancreatic exocrine differentiation. There was no clinical or radiologic evidence of primary pancreatic or head and neck tumors. After surgical resection of the tumor, there was no recurrence or metastasis during 33 months follow-up.
In this report, we have presented a rare case of primary pure pancreatic-type acinar cell carcinoma arising in the stomach and suggest that it could be helpful if the pathologist were aware that pancreatic-type acinar cell carcinoma could arise in the stomach as a polypoid submucosal tumor in the routine diagnostic field of gastric endoscopy.
KeywordsAcinar cell carcinoma Heterotopic pancreas Stomach
Although, pancreatic neoplasms can occur in any of the sites where heterotopic pancreatic tissue is present, the incidence of extrapancreatic pancreatic-type neoplasms is very rare; most are ductal adenocarcinomas and there have been only a few cases of pancreatic-type acinar cell carcinoma (ACC) [1–5]. ACC is also rare in the pancreas and represents approximately 1–2 and 15% of exocrine pancreatic neoplasms in adults and children, respectively . To date, there have been eight reported cases of pure pancreatic-type ACCs located at extra-pancreatic sites and five of which arose in the stomach [1–5]. Herein, we present the sixth case of pure form of primary pancreatic-type ACC arising in the stomach. Informed consent was provided by the patient according to the Declaration of Helsinki.
Summary of Reported Cases of Pure Form Pancreatic-Type Acinar Cell Carcinomas Arising in the Stomach
Ectopic pancreatic tissue
Sun and Wasserman, 2004.
exophytic polypoid mass with ulcer
trypsin +, chymotrypsin +, A1AT f+, A1ACT f+, CD56 -, Syn -, Cg -, gastrin -
pure gastric form
Mizuno et al., 2007.
GIST or lymphomac, IIBp
submucosal mass invading pancreatic head
liver metastasis at 7 months, alive after 11 months
Ambrosini-Spaltro et al., 2009.
low mitotic index
A1AT +, Cg -, Syn -, gastrin -
presence by pancreatic metaplasia
exophytic polypoid mass with ulcer
trypsin +, A1AT +, CD56 f+, Syn w+, Cg -, serotonin -, insulin -, glucagon -
pure gastric form
died from complications after 1 month
Yonenaga et al., case 2, 2016.
chymotrypsin +, A1ACT +, Cg f+, Syn f+, insulin -, glucagon -, gastrin -, somatostatin -
pure gastric form
died from coexisting advanced PaDA after 5 months
Present case, 2016
GIST or lymphomac, IIBp
exophytic polypoid mass
A1AT +, A1ACT +, CD56 w+, DOG1 w+, Syn -, Cg -, TTF-1 -, CD34 -, c-Kit -
laparoscopic wedge resection
pure gastric form
alive without disease after 33 months
Because of rarity of extra-pancreatic ACC, the diagnosis of ACC could be challenging. In such cases, immunohistochemical detection of acinar differentiation, with markers such as trypsin, chymotrypsin, lipase, and amylase is helpful in the diagnosis of ACC [1–8]. However, if there are substantial amounts of endocrine or ductal components (more than 25% of the tumors) mixed carcinomas should be distinguished  and trypsin-positivity also seen in gastric neuroendocrine tumors . Therefore, evaluation of neuroendocrine markers is needed to diagnose the pure form of ACC. Strong immunoreactivity for pancreatic exocrine enzymes along with negativity for neuroendocrine markers indicates ACC [1–5]. However, weak or focal expression of neuroendocrine markers, such as chromogranin, synaptophysin, and CD56 have also been observed (cases 4, and 5 in Table 1) [1, 5]. In our case, although the intensity of the expression was weak, the tumor cells were positive for CD56. Therefore, in addition to a neuroendocrine tumor, a mixed acinar-neuroendocrine carcinoma should also be considered during diagnosis. However, the tumor cells were completely negative for other common neuroendocrine markers such as chromogranin A, synaptophysin, and TTF-1. Moreover, acinar differentiation of the tumor cells was indicated by strong immunoreactivity for α1-antitrypsin, chymotrypsin, and α1-antichymotrypsin and there were no definitive endocrine components as a part of mixed carcinoma. In addition, the expression of CD56 could be seen in various types of non-neuroendocrine tumors . Therefore, we could make a diagnosis of pure ACC. In addition, one interesting finding during the diagnostic approach for the gastric pancreatic-type ACC is that the initial diagnosis of the endoscopic biopsy was poorly differentiated adenocarcinoma in four cases (cases 1, 3, 4, and 5) [1, 2, 4, 5]. In two cases (cases 2 and 6), initial biopsies were inconclusive and radiologic findings suggested gastrointestinal stromal tumor or malignant lymphoma . These findings suggest that if there are tumor cells with acinar differentiation in gastric mucosal biopsies, immunohistochemical staining for pancreatic exocrine differentiation might be helpful for diagnosis, especially for tumors presenting as polypoid and/or submucosal tumors.
Concerning the origin of pancreatic-type ACC in the stomach, it has been suggested that it originates from pancreatic metaplasia or heterotopic pancreatic tissue. Among the five previously reported cases of gastric ACCs, one case had metaplastic pancreatic tissue in the adjacent gastric mucosa . However, metaplastic pancreatic tissue is not mentioned nor identified in the other cases of primary pure ACC of the stomach (cases 1, 2, 4, 5, and 6 in Table 1) [2–5]. Therefore, the possibility that gastric ACC derived from the gastric heterotopic pancreas was suggested. As we have summarized in Table 1, the six cases of primary pure ACC of the stomach, including our case, were suspected to have originated from heterotopic pancreatic tissue. This assumption was based on the fact that heterotopic pancreas is usually located in the submucosa  and that in three cases (cases 1, 2, and 6) it was also located mainly at the submucosa and pancreatic metaplasia was not identified in most cases [2–5]. However, the possibility that ACC is derived from heterotopic pancreatic tissue is also questionable. In five cases of pure pancreatic-type ACC in the stomach (cases 1, 2, 4, 5, and 6), ectopic pancreatic tissue was not identified and there was no evidence of tumors in locations other than the stomach, such as in the pancreas or the head and neck area in four cases [2–5]. Therefore, although it is not difficult to define the origin of ACC of the stomach, this type of tumor might be regarded as a primary gastric tumor and separately considered from the pancreatic ACC. In addition, further investigation of additional cases is needed to define the exact nature of pancreatic-type ACC in the stomach.
Although pancreatic ACC is not as lethal as pancreatic ductal adenocarcinoma, it has also been reported as one of the most aggressive malignant tumors . The median survival of pancreas ACC patients with localized disease and metastatic disease is 38 and 14 months, respectively . However, the prognosis of primary ACC of the stomach is not clear because of the limited number of cases, and the outcomes are not clear even in the cases that have been reported. As we summarized in Table 1, although there was no cancer-specific outcomes of the patients, partial gastrectomies were performed in two cases and subtotal gastrectomies were performed in one case as therapeutic operations [1, 2, 4]. One patient that underwent partial gastrectomy died 1 month after the operation from complications . Recently, there was a report of an autopsy case of gastric ACC accompanied advanced pancreatic ductal adenocarcinoma metastasized to lymph node, liver, and peritoneum . Therefore, it was difficult to assume the biologic behavior of gastric ACC. Another report showed that even a patient with a tumor that had invaded the pancreas and metastasized to lymph nodes was alive 11 months after an operation, despite metastatic relapse in the liver at 7 months after operation . In our case, the patient has been disease-free for 33 months after a limited surgical procedure, laparoscopic wedge resection. The relatively limited progression of our case might be due to early detection of the tumor by endoscopy during a medical check-up. These findings suggest that prognosis might be related with stage of tumor as it is with primary pancreatic ACC .
In conclusion, we have presented a rare case of primary pure pancreatic-type ACC arising in the stomach. Although it is difficult to consider gastric ACC in the routine diagnostic field of gastric mucosal biopsy due to its rarity, it could be helpful if the pathologist were aware that pancreatic-type ACCs could arise in the stomach as a polypoid submucosal tumor. In addition, if a tumor has the acinar architectural pattern, a check for the pancreatic exocrine differentiation might be helpful in diagnosis.
Acinar cell carcinoma
We thank Dennis B. Leveson-Gower who provided medical writing services.
This work was supported by a National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No. 2008–0062279).
Availability of data and materials
The dataset supporting the conclusions of this article is included within the article.
KMK, CYK, SMH, and KYJ make a diagnosis and contributed to conception and design. CYK performed follow up of patients and collected data. KMK and SMH performed immunohistochemical staining. KMK, CYK, SMH, and KYJ wrote manuscript and approved final version of manuscript.
The authors declare that they have no competing interests.
Consent for publication
Written informed consent was obtained from the patient for publication of this Case Report and any accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.
Ethic approval and consent to participate
Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
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