Localized type 1 autoimmune pancreatitis superimposed upon preexisting intraductal papillary mucinous neoplasms

Abstract

A 70-year-old woman was found to have 2 cystic lesions in the head of the pancreas on abdominal ultrasonography during a routine medical examination. Endoscopic ultrasonography (EUS) and magnetic resonance cholangiopancreatography showed multilocular cysts in the head of the pancreas without dilation of the main pancreatic duct. The patient was followed-up semiannually with imaging studies for suspected branch duct-type intraductal papillary mucinous neoplasm (IPMN). At 3 years after initial presentation, hypoechoic lesions were observed around each pancreatic cyst by EUS. Diffusion-weighted imaging showed high-intensity regions corresponding to these lesions. Therefore, a diagnosis of invasive carcinoma derived from IPMN could not be excluded, and subtotal stomach-preserving pancreaticoduodenectomy was performed. The macroscopic examination of the surgical specimen showed whitish solid masses in the head of the pancreas, with multilocular cysts within each mass. Microscopically, each solid mass consisted of inflammatory cells such as lymphocytes and plasma cells. Furthermore, immunochemical staining revealed immunoglobulin G4-positive cells, and many obliterating phlebitides were observed. The cysts consisted of mucus-producing epithelial cells and showed a papillary growth pattern. Based on these findings, we diagnosed multiple localized type 1 autoimmune pancreatitis occurring only in the vicinity of the branch duct-type IPMN.

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.…”

Mucinous Cystic Neoplasm of the Pancreas With Increased IgG4+ Plasma Cells and Histopathologic Features of Autoimmune Pancreatitis/IgG4—Related Disease

“…Although some authors proposed that IPMN may develop in a background of AIP based on the presence of lymphoplasmacytic infiltration with abundant plasma cells and storiform fibrosis at a location distant from IPMN, 6 other hypothesized that the histologic changes consistent with type 1 AIP may be a secondary phenomenon that appeared several years after IPMN. 7,8 The characteristic feature common to both pancreatic MCN and IPMN is mucin production. We have recently described that the sclerosing variant of mucoepidermoid carcinoma of salivary glands is associated with increased IgG4+ plasma cells.…”

“…1,2 Dense lymphoplasmacytic infiltrates with elevated IgG4+ plasma cells have also been described in several pancreatic neoplasms, including pancreatic ductal adenocarcinoma and intraductal papillary mucinous neoplasm (IPMN). [3][4][5][6][7][8] We report the first case of a pancreatic mucinous cystic neoplasm (MCN) with histopathologic features of type 1 AIP/IgG4-RD localized to the cyst wall.…”

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

“…However, there have been some reports regarding the involvement of autoimmune pancreatitis (AIP) in patients with IPMN who underwent surgery following a preoperative diagnosis of suspected invasive carcinoma derived from IPMN or PDAC (3,4). Interestingly, the possibility of AIP as a paraneoplastic syndrome has recently been reported (5).…”