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A 50-year-old man presented to the emergency department with left chest pain, epigastralgia, and low-grade fever for several days. A CT scan showed left pleural effusion, ground-glass opacities in the lower lobes of both lungs, and a capsule-like rim in the pancreas. ERCP showed narrowing of the main pancreatic duct. EUS-FNA was performed, but pathological findings showed no IgG4-positive cells. A thoracoscopic biopsy was performed, and pathological findings showed many IgG4-positive cells. A diagnosis of autoimmune pancreatitis and IgG4-associated pleurisy was made according to international diagnostic criteria. After that, oral steroid therapy was started, and left pleural effusion and pancreatic enlargement improved., (© 2023. Japanese Society of Gastroenterology.)

Mixed acinar-neuroendocrine carcinoma (MAEC) of the pancreas is a rare entity, and obtaining a preoperative diagnosis is difficult. We report a case of pancreatic MAEC successfully diagnosed with EUS-FNA. The case was a 72-year-old male with upper abdominal pain. Abdominal CT showed an irregular, hypovascular tumor of pancreatic tail. EUS-FNA was performed using a 22G needle. Immunostaining revealed positive results for the acinar marker trypsin and the neuroendocrine markers chromogranin A and synaptophysin. The possibility for MAEC was considered. He underwent distal pancreatectomy and splenectomy. Immunohistochemical examination of the tumor cells showed a wide range of positivity for bcl-10 and trypsin as well as for chromogranin A and synaptophysin, but negative results for CA19-9 and AFP. Considering that ≥ 30% tumors were positive for both acinar and neuroendocrine markers, the patient was diagnosed with MAEC.

Pancreatic schwannoma is difficult to diagnose preoperatively. A 79-year-old man was found to have a 9-mm pancreatic mass on abdominal ultrasonography. On EUS, there was a 9-mm, clearly demarcated, round, solid, hypo-echoic mass in the pancreatic body. The differential diagnosis included a pancreatic neuroendocrine tumor, a solid-pseudopapillary neoplasm, and an atypical pancreatic cancer. EUS-FNA was performed with a 22G needle. On pathology examination, spindle-shaped tumor cells were seen proliferating in bundles. On immunostaining, the lesion was negative for c-kit, CD34, and α-SMA but positive for S-100 protein. The MIB-1 index was < 2%. Based on the above findings, the lesion was diagnosed as a benign pancreatic schwannoma. We, therefore, decided to follow the patient with careful observation rather than resecting the lesion surgically. The tumor has not changed significantly after 3 years of follow-up. EUS-FNA is useful for the diagnosis of pancreatic schwannoma. If the tumor can be determined to be benign preoperatively, unnecessary surgery can be avoided. EUS-FNA should be actively implemented for pancreatic tumors that are difficult to diagnose definitively on imaging.

A 66-year-old man who was on oral medication for type 2 diabetes experienced a rapid decline in glycemic control (increase in glycosylated hemoglobin level from 7.7 to 10.2% over 3 months). Abdominal ultrasonography revealed a 20-mm hypoechoic mass in the pancreatic tail. Serum tumor marker carbohydrate antigen 19-9 and DUPAN2 levels were within the respective normal ranges; serum IgG4 level was also normal at 21.8 mg/dL. Abdominal contrast computed tomography revealed a 26-mm tumor in the pancreatic tail. Magnetic resonance cholangiopancreatography revealed disruption of the main pancreatic duct and dilation of the caudal pancreatic duct. Endoscopic ultrasonography revealed a near-round-shaped hypoechoic mass with interspersed hyperechoic areas. Endoscopic ultrasonography-guided fine needle aspiration was performed using a 22-G needle, but no malignant findings were observed. There were no signs of sialadenitis, retroperitoneal fibrosis, nephropathy, or other conditions associated with IgG4-related diseases. Distal pancreatectomy was performed; a 23-mm white mass was resected from the pancreatic tail. A histopathological examination showed advanced inflammatory cell infiltration mainly involving lymphocytes/plasma cells along with storiform fibrosis and obliterative phlebitis. No more than five IgG4-positive cells were observed per high-power field. These were level 1 pathological findings, and a definitive diagnosis of type 1 autoimmune pancreatitis (AIP) was made according to the International Consensus Diagnostic Criteria. Type 1 AIP associated with normal serum IgG4 levels and absence of IgG4-positive cells on histological examination is a rare clinical entity, which is very difficult to distinguish from pancreatic cancer. Here we report such a case and present a review of the relevant literature.

The patient was a 60-year-old man without any particular complaints, but he underwent abdominal computed tomography (CT) and magnetic resonance cholangiopancreatography (MRCP) due to a fatty liver, which revealed two similar cystic lesions regarded as branch duct-type intraductal papillary mucinous neoplasm (BD-IPMN) in the pancreatic body [BD-IPMN (b), 16 mm in size] and tail [BD-IPMN (t), 13 mm in size] without a "high-risk stigmata" or "worrisome features". He subsequently received follow-up by MRCP every 6 months. Two years later, MRCP showed prominent dilation of the main pancreatic duct (MPD) and mural nodule formation within the dilated MPD adjacent to the BD-IPMN (b). Distal pancreatectomy specimens revealed that the BD-IPMN (b) was lined by low-papillary gastric mucinous epithelium with low-to-intermediate-grade dysplasia and involved the MPD, forming a malignant mural nodule showing pancreatobiliary-type IPMN. In contrast, the BD-IPMN (t) was lined by flat, monolayer columnar gastric mucinous epithelium without atypia, which suggested the possibility of a "simple mucinous cyst". A genetic analysis showed KRAS mutation only in BD-IPMN (b). Differences in the histological and genetic findings between two similar BD-IPMNs in the present case may suggest what kinds of examinations should be performed in patients with BD-IPMNs without any worrisome features.

The case patient was a previously healthy 82-year-old male. Abdominal ultrasound during a medical check-up revealed a dilatation of the main pancreatic duct, and the patient was referred to our hospital for closer examination. Contrast-enhanced computed tomography (CT) revealed a low-density mass of 20 mm in the pancreatic head-body transitional area. Magnetic resonance cholangiopancreatography (MRCP) revealed marked dilatation of the main pancreatic duct and branches in the body-tail. On endoscopic ultrasonography (EUS), a hypoechoic mass with irregular shape was detected, which was consistent with the area of pancreatic duct stenosis. Endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) and pancreatic juice cytology were performed; however, there were no malignant findings. Serum IgG4 levels had increased to 299 mg/dL. Cancer of the pancreatic head was suspected and a pancreaticoduodenectomy was thus performed. Macroscopic findings included a white mass with indistinct border in the constricted part of the pancreatic duct and mottled fatty replacement of the pancreatic head. Pathologically, a large amount of IgG4-positive plasma cells was found in the white mass, with storiform fibrosis and obstructive phlebitis, which led to the diagnosis of type 1 autoimmune pancreatitis (AIP). Furthermore, scattered low-high grade pancreatic intraepithelial neoplasia lesions were observed throughout the pancreatic head, separately from the AIP lesion. This is an interesting case that suggests an association between AIP and pancreatic cancer. We report the case with a review of relevant literature.

Mucinous cystic neoplasm of the liver (MCN-L) is a very rare tumor whose detailed behavior is still unknown. We describe two cases of MCN-L that exhibited extremely interesting growth patterns, and discuss the characteristics of MCN-Ls. Both cases exhibited MCN-L that originated from the left hepatic lobe (Segment 4) and then prolapsed into the left hepatic duct and common bile duct, resulting in obstructive jaundice due to expansive growth. Endoscopic retrograde cholangiopancreatographies showed the characteristic oval-shaped filling defects in the bile ducts. Endoscopic ultrasound and intraductal ultrasound were useful for differentiating the tumors from stones, since multiple septal formations were observed inside the tumors. A literature search revealed that, over the past 10 years, 15 cases of MCN-L (biliary cystadenomas with ovarian-like stroma) that showed expansive growth in the bile duct had been reported. Prolapse into the bile duct and expansive growth appear to be characteristic behavior of MCN-L. In the future, additional data on more cases needs to be collected to further elucidate MCN-L pathophysiology.