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.

Multilocular Cyst of Type 1 Autoimmune Pancreatitis Masquerading as Cancerization of Intraductal Papillary Mucinous Neoplasm

“…In our case, IgG4-positive cells infiltrated around the ductal epithelium and formed so-called ductitis (Fig. 5), similar to the previous studies (1,(7)(8)(9)(10)(11)(12)(13)(14). All of these aspects are suggestive of and compatible with the development of autoimmunity against the mucin-secreting pancreatic epithelia, or IPMN.…”

“…To date, only a few studies (1-3) and several case reports have described the coexistence of pancreatic cysts [e.g., IPMN (8-10) or IPMN-like lesions (11,12)] and IgG4related pathology (infiltration by type 1 AIP or IgG4positive cell) (1,(7)(8)(9)(10)(11)(12)(13)(14). Among the 9 reported cases with coexisting type 1 AIP and BD-IPMN (Table), 5 simultaneous cases were detected (cases: 1, 2, 5, 6 and 8) and 4 cases of AIP developed during follow-up for an IPMN or IPMN-like lesion (case: 3, 4, 7, and 9) (8,9). Although the number of reported cases was limited, macroscopically visible IgG4related lesions appeared in the background of IPMNs or IPMN-like lesions, but not in the opposite order.…”

“…The most accurate diagnostic approach for pancreatic mass lesions is histological confirmation by EUS-FNA (18); however, care should be taken as there is a risk of dissemination in cases of cystic lesions (17). Koshita et al (9) reported a case of type 1 AIP accompanied by BD-IPMN that was safely diagnosed by EUS-FNA without surgical resection (case: 7). Pancreatic juice cytology is also helpful; how-ever, the sensitivity for malignancy is limited (33-67%) and some patients develop post-ERCP pancreatitis ( 3-25%) (19,20).…”

Steroid Therapy and Steroid Response in Autoimmune Pancreatitis

“…These include a 9 mm, well-demarcated pancreatic mass that was not affecting the main pancreatic duct [57]; a 2 cm mass protruding inside the main pancreatic duct and mimicking a main duct-type intraductal papillary mucinous neoplasm (IPMN) [58,59]; a 3 cm, low-echoic mass concomitant with a branch-type IPMN [60]; a multilocular cyst with progression of symmetric wall thickening during the time course mimicking cancerization of a branch-type IPMN [61]; and a pancreatic mass invading the ascending colon and mimicking invasive pancreatic carcinoma [62]. Many of these lesions were not accurately diagnosed, but some did not undergo unnecessary resection due to a negative workup for malignancies using EUS-FNAB and the sequential confirmation of a steroid response [60,62]. We should also bear in mind the possible occurrence of AIP or AIP-like pancreatitis due to treatment using an immune checkpoint inhibitor [63].…”

Signet-ring Cell Carcinoma Derived from a Main Duct-type Intraductal Papillary Mucinous Neoplasm of the Pancreas: A Case Report with Long-term Follow-up

“…In this patient, mass forming pancreatitis in the pancreatic tail, which existed separately from the MD-IPMN in the pancreatic body, was also detected. Some reports have described the development of autoimmune pancreatitis (AIP) around IPMNs ( 19 , 20 ), whereas a literature search revealed no cases of IPMN involving mass forming pancreatitis without AIP. Considering that some cases of IPMN develop acute pancreatitis due to obstruction of the MPD by mucin production, a mechanism like this might have brought about the change of chronic pancreatitis in the present case, followed by the development of mass-forming pancreatitis.…”