Intraductal papillary mucinous neoplasm with specific fibroinflammatory pancreatitis: a rare but potential mimicker of malignant transformation

A 57-year-old male made a regular follow-up visit for hepatic hemangioma at a local hospital. Abdominal ultrasound incidentally revealed a hypo-echoic area in the head of the pancreas. ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (CT) showed cystic dilatation partially communicating with the main pancreatic duct. Part of the lesion demonstrated increased ¹⁸F-FDG uptake (maximum standardized uptake value of 4.1) suggesting malignant potential. The patient presented to our outpatient clinic. Contrast-enhanced abdominal magnetic resonance imaging (MRI) revealed multiple round lesions in the pancreatic head, each communicating with the pancreatic duct (Figure 1A,1B), raising the concern for a branch-duct intraductal papillary mucinous neoplasm (IPMN). Serum levels of carcinoembryonic antigen, carbohydrate antigen 19-9 (CA19-9), and carbohydrate antigen 125 were within normal range. The serum immunoglobulin G4 (IgG4) level was markedly elevated (6,040 mg/L, normal range: 80–1,400 mg/L). Contrast-enhanced ultrasound of the pancreas manifested a cystic-solid mass, with a predominantly solid component that showed arterial phase enhancement, raising concern for possible malignancy. Endoscopic ultrasonography revealed a 3.2 cm × 1.8 cm hypoechoic cystic-solid lesion in the pancreatic head, characterized by a predominant solid component and multiple internal microcysts (Figure 1C). The upstream pancreatic duct at the pancreatic neck was mildly dilated with a maximal diameter of 4.6 mm, whereas no dilatation of common bile duct was detected. The patient subsequently underwent a Whipple procedure. Postoperative pathology confirmed a gastric-type IPMN with low-grade dysplasia (Figure 1D). No invasive carcinoma was identified. Additionally, prominent lymphoid follicles with germinal centers were observed in the tumoral stroma, adjacent normal pancreatic parenchyma, and peripancreatic adipose tissue. The possibility of concurrent autoimmune pancreatitis (AIP) was ruled out according to the International Consensus Diagnostic Criteria and a final diagnosis of follicular pancreatitis (FP) was established (1).

Figure 1 Coexistence of intraductal papillary mucinous neoplasm with specific fibroinflammatory pancreatitis. (A,B) Contrast-enhanced MRI showed multiple round cystic lesions in the pancreatic head, each communicating with the pancreatic duct. (C) Endoscopic ultrasound demonstrated a hypoechoic cystic-solid lesion with a predominant solid component and multiple internal microcysts. (D) Hematoxylin-eosin-stained micrograph revealed IPMN coexisted with follicular pancreatitis (20× magnification). (E) MRI showed multiple cystic lesions in the pancreatic head communicating with a dilated main pancreatic duct. (F) Contrast-enhanced CT revealed an enlarged pancreatic head with an irregular hypodense lesion, no post-contrast enhancement, and irregular dilatation of the main pancreatic duct. (G) Hematoxylin-eosin-stained micrograph revealed IPMN coexisted with lymphoplasmacytic sclerosing pancreatitis (25× magnification). (H) IgG4 staining confirmed the diagnosis of IgG4-related type 1 autoimmune pancreatitis (400× magnification). CT, computed tomography; IgG4, immunoglobulin G4; IPMN, intraductal papillary mucinous neoplasm; MRI, magnetic resonance imaging.

The second case was a consultation from an outside institution. A 59-year-old male underwent a Whipple procedure for a pancreatic mass at the outside institution. Contrast-enhanced abdominal MRI showed multiple cystic lesions communicating with a dilated main pancreatic duct (Figure 1E), which indicated IPMN with potential chronic pancreatitis. Contrast-enhanced abdominal CT revealed an enlarged pancreatic head with an irregular hypodense lesion measuring approximately 26 mm in its longest diameter. The lesion demonstrated no post-contrast enhancement, and the main pancreatic duct was irregularly dilated (Figure 1F). The serum IgG4 and CA19-9 levels were within the normal range. After reviewing the hematoxylin-eosin and immunostained slides, diagnoses of gastric-type IPMN with focally high-grade dysplasia and concomitant IgG4-related type 1 AIP were established (Figure 1G,1H).

The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the institutional ethics committee of Peking Union Medical College Hospital (No. I-23PJ122) and individual consent for this retrospective analysis was waived.

Coexistence of IPMN and specific forms of FP is rarely encountered. There were several reports of IPMN concomitant with type 1 AIP (2-4), although some were not pathologically confirmed (4). FP, as proposed by Zen et al., may mimic malignancy even in the absence of IPMN or pancreatic cancer possibly due to the metabolically active lymphoid follicles (1,5,6). To our knowledge, our case was the first reported case of low-grade gastric-type IPMN coexisting with FP. The “chicken-and-egg” question of such coexistence remained unclear. However, it is noted that IgG4⁺ plasma cells can be detected in IPMN lesions (2,7). Moreover, IPMN might have partially shared immune signature (e.g., T helper 2 cells as in AIP and T helper 17 cells as in FP), which could facilitate the development of both diseases (8-10). IPMN coexisting with FP or AIP should be considered in the differential diagnosis when malignant transformation of IPMN is suspected.

Acknowledgments

None.

Footnote

Provenance and Peer Review: This article was a standard submission to the journal. The article has undergone external peer review.

Peer Review File: Available at https://hbsn.amegroups.com/article/view/10.21037/hbsn-2025-460/prf

Funding: This study was supported by CAMS Innovation Fund for Medical Sciences (CIFMS) (No. 2023-I2M-C&T-B-003 to X.C.) and National High Level Hospital Clinical Research Funding (No. 2022-PUMCH-D-001 to X.C.).

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://hbsn.amegroups.com/article/view/10.21037/hbsn-2025-460/coif). X.C. reports grants from CAMS Innovation Fund for Medical Sciences (CIFMS) (No. 2023-I2M-C&T-B-003) and National High Level Hospital Clinical Research Funding (No. 2022-PUMCH-D-001). The other authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the institutional ethics committee of Peking Union Medical College Hospital (No. I-23PJ122) and individual consent for this retrospective analysis was waived.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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