Branch Duct Intraductal Papillary Mucinous Neoplasms of the Pancreas Involving Type 1 Localized Autoimmune Pancreatitis with Normal Serum IgG4 Levels Successfully Diagnosed by Endoscopic Ultrasound-guided Fine-needle Aspiration and Treated without Pancreatic Surgery

Abstract

We herein report a 68-year-old man with branch duct intraductal papillary mucinous neoplasms of the pancreas (BD-IPMNs) involving type 1 localized autoimmune pancreatitis (AIP) with normal serum IgG4 levels. Although he was referred to our medical center due to suspicion of pancreatic cancer concomitant with BD-IPMNs, endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) revealed a mass suspected of being pancreatic cancer to be type 1 AIP. Steroid administration notably reduced the mass. Although the clinical diagnosis of pancreatic masses in patients with IPMN can be occasionally challenging, performing a pathological examination by EUS-FNA may prevent unnecessary pancreatic surgery in cases of possible AIP.

Keywords: autoimmune pancreatitis (AIP); endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA); intraductal papillary mucinous neoplasms of the pancreas (IPMN).

Figure 1.

On CECT (axial) before a steroid trial, a mass lesion about 3 cm in size detected in the pancreatic body showed low density in the early phase (a) and homogenous delayed enhancement in the portal (b) and late (c) phases.

Figure 2.

The findings of imaging studies before a steroid trial were as follows: a: On diffusion-weighted images, the mass lesion in the pancreatic body showed a high signal. b: MRCP showed stenosis of the MPD in the pancreatic body, upstream MPD dilation 3 mm in diameter, and multiple pancreatic cysts considered to be BD-IPMNs in the pancreatic tail. c: EUS visualized a 3-cm-diameter low echoic mass with a heterogeneous internal echo structure in the body of the pancreas. d, e: On EUS, suspected BD-IPMNs were also detected in the pancreatic body and tail apart from the mass lesion. d shows small pancreatic cysts in the pancreatic body (arrowhead, cyst; arrow, main pancreatic duct) and e shows a multilocular pancreatic cyst more than 30 mm in size without a mural nodule in the pancreatic tail. f: On ERP, obstruction of the MPD in the pancreatic body was detected, and the upstream MPD could not be visualized.

Figure 3.

a: Hematoxylin and Eosin staining (40×). The specimen was fibrotic with infiltration of many lymphocytes and plasmacytes. b: LCA staining (40×). Many LCA-positive cells diffusely infiltrated the fibrotic lesion of the specimen. c: IgG4 staining (40×). Infiltration of abundant (≥10 cells/HPF) IgG4-positive cells in the fibrotic lesion of the specimen was detected. d: Elastica-Masson staining (100×). Obliterative phlebitis was detected.

Figure 4.

a-c: CECT (axial) after the initial administration of prednisolone (a: 2 weeks after, b: 2 months after, c: 5 months after) showed the mass lesion in the pancreatic body to be notably reduced in size, and the enhancement patterns of this mass lesion on CECT returned to those of the normal pancreas. d: ERP after a steroid trial revealed improvement of the MPD obstruction in the pancreatic body, visualization of the MPD up to the pancreatic tail and communication of the MPD with the 30-mm BD-IPMN in the pancreatic tail.