Case Report
Copyright ©The Author(s) 2021. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Jul 28, 2021; 27(28): 4738-4745
Published online Jul 28, 2021. doi: 10.3748/wjg.v27.i28.4738
HER2-positive adenocarcinoma arising from heterotopic pancreas tissue in the duodenum: A case report
Yoshifumi S Hirokawa, Takashi Iwata, Yoshinaga Okugawa, Koji Tanaka, Hiroyuki Sakurai, Masatoshi Watanabe
Yoshifumi S Hirokawa, Masatoshi Watanabe, Department of Oncologic Pathology, Mie University Graduate School of Medicine, Mie 5148507, Japan
Takashi Iwata, Cancer Center, Aichi Medical University, Aichi 4801195, Japan
Yoshinaga Okugawa, Department of Genomic Medicine, Mie University Hospital, Mie 5148507, Japan
Koji Tanaka, Department of Surgery, IGA City General Hospital, Mie 5180823, Japan
Hiroyuki Sakurai, Hepato-biliary-pancreatic and Transplant Surgery, Mie University Hospital, Mie 5148507, Japan
Author contributions: Hirokawa YS contributed to pathological diagnosis and manuscript drafting; Tanaka K and Sakurai H performed surgery; Iwata T and Okugawa Y contributed to medical treatment; Watanabe M was responsible for the manuscript revision; all authors made final approval for the manuscript to be submitted.
Informed consent statement: Written informed consent to publish the clinical details and images was obtained from the patient.
Conflict-of-interest statement: All authors declare no conflicts of interest.
CARE Checklist (2016) statement: The authors have read the CARE Checklist (2016), and the manuscript was prepared and revised according to the CARE Checklist (2016).
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See:
Corresponding author: Yoshifumi S Hirokawa, MD, PhD, Lecturer, Department of Oncologic Pathology, Mie University Graduate School of Medicine, 2-174 Edobashi, Tsu, Mie 5148507, Japan.
Received: May 7, 2021
Peer-review started: May 7, 2021
First decision: June 6, 2021
Revised: June 15, 2021
Accepted: July 9, 2021
Article in press: July 9, 2021
Published online: July 28, 2021

Adenocarcinoma originating from heterotopic pancreas tissue is a rare disease. Furthermore, to our knowledge, no HER2-positive cases in the duodenum have been reported in the scientific literature nor has the efficacy of trastuzumab treatment for the disease been reported.


A 65-year-old woman whose clinical diagnosis was unresectable advanced duodenal cancer with HER2 overexpression responded well to trastuzumab chemotherapy. The main tumor in the duodenum reduced drastically. The patient underwent pancreaticoduodenectomy and lymph node dissection. A small number of cancer cells remained in the submucosal layer of the duodenum and pancreas head. After histological and immunohistochemical examination, the patient was diagnosed with duodenal adenocarcinoma originating from heterotopic pancreas tissue.


Trastuzumab treatment is effective in HER2-positive adenocarcinoma originating from heterotopic pancreas tissue in the duodenum.

Keywords: Heterotopic pancreas tissue, Duodenal cancer, Human epidermal growth factor receptor 2, Trastuzumab, Conversion surgery, Case report

Core Tip: Adenocarcinoma that develops from heterotopic pancreas tissue in the duodenum is a very rare disease. Therefore, standard chemotherapy regimens to treat these patients have not been established. A 65-year-old woman presented with unresectable duodenal cancer with HER2 overexpression. Because the patient responded well to trastuzumab chemotherapy, pancreatoduodenectomy was performed. Histology and immunohistochemistry assessments revealed that the cancer developed from heterotopic pancreas tissue in the duodenum. The findings of this case suggest that HER2 status should be examined in duodenal adenocarcinoma to determine the indication for targeted therapy. Trastuzumab chemotherapy is effective for heterotopic pancreatic adenocarcinoma but not orthotopic pancreatic cancer.