Recent studies suggested the existence of two subtypes of autoimmune pancreatitis (AIP): type 1 related with IgG4 as the pancreatic manifestation of IgG4-related disease (IgG4-RD), and type 2 related with a granulocytic epithelial lesion. The characteristic features of type 1 AIP are increased serum IgG4 levels, abundant infiltration of IgG4+plasmacytes and lymphocytes, storiform fibrosis, and obliterative phlebitis, extra-pancreatic manifestations of IgG4-RD (eg. sclerosing cholangitis, sclerosing sialadenitis, retroperitoneal fibrosis), and steroid responsiveness. T helper type 2 (Th2) immune responses seem to be dominant over Th1 in type 1/IgG4-RD. Although disease specific target antigens still remain unclear, we have suggested that disease-related autoantibodies such as carbonic anhydrase II, lactoferrin, and PSTI, all of which are distributed in exocrine organs, are potential candidates. Recent human and experimental animal studies have suggested a possible involvement of innate immunity in addition to acquired immunity, such as genetic background, bacterial/viral infections, complement activation via classical pathway, or IgG4-production of monocytes/basophils with TLR/NOD stimulation. Based on these findings, we have proposed a hypothesis for the development of type 1 AIP, one of the IgG4-RD.

Resectability criteria for pancreatic cancer have been established by the NCCN guidelines and have been implemented in our clinics, however, these are revised annually and we address certain issues. The 7^th edition of the JPS guidelines was published last year and the tumor extent (T), the lymph node metastasis (N) and stage classification were revised in order to maintain the compatibility with those of the 7^th UICC guidelines. Also, new criteria for histological response and original resectability criteria for Japan are proposed. Based on these new resectability criteria, the survival outcomes in our resected pancreatic cancer patients without neoadjuvant therapy were analyzed. As a result, the definition of borderline resectable pancreatic cancer based on the degree of portal system invasion (abutment/contact) is shown to be valid. Compared to the NCCN guidelines, the new resectability criteria is written much more clearly and concisely, and is very useful for decision-making and use in clinical trials.

We reported the clinicopathological characteristics of patients with borderline resectable (BR) pancreatic carcinoma who underwent surgical resection at our institution and discussed on the therapeutic strategies of BR pancreatic carcinoma. In an analysis of patients with BR pancreatic carcinoma that underwent upfront surgery at our institution, patients with BR pancreatic carcinoma had more advanced tumor including larger tumor size and higher rate of nodal involvement and worse overall survival compared with patients with resectable pancreatic carcinoma. Especially, patients with BR pancreatic carcinoma with arterial contact had much worse survival due to lower rate and less effectiveness of adjuvant chemotherapy. Neoadjuvant chemotherapy for patients with BR pancreatic carcinoma significantly improved the rate of R0 resection and overall survival compared with those of patients who underwent upfront surgery. Neoadjuvant chemotherapy is essential for patients with BR pancreatic carcinoma to improve overall survival of these patients. However, further prospective studies are needed to establish optimal therapeutic strategies for BR pancreatic carcinoma.

Preoperative treatment has been implemented to improve the survival rate of borderline resectable (BR) pancreatic cancer, but specific recommendations have not been established for treatment policies. In order to grasp the current state of the treatment policy for BR pancreatic cancer in Japan, an audit questionnaire was administered to participating institutions of the Japanese Society of Pancreatic Surgery and responses were obtained from 74 institutions. Many institutions conducted preoperative treatment in both BR-A and BR-PV, but 23 institutions (33%) treated with BR-PV with upfront surgery. For preoperative treatment, 27 institutions (57%) used chemotherapy and 20 institutions (43%) used chemoradiotherapy for BR-PV. GEM+nabPTX was the most frequent chemotherapy regimen at 14 institutions, and S-1+radiation therapy or GEM+S-1+radiation therapy was utilized at 7 institutions. Preoperative treatment for BR-A pancreatic cancer was almost the same as for BR-PV. However, for BR-PV, approximately one-third of the institutions treated with upfront surgery.

FOLFIRINOX and gemcitabine plus nab-paclitaxel (GnP) have been shown to improve the prognosis of patients with metastatic pancreatic cancer (PC). However, there are no clinical trials that directly compare the efficacy of these two regimens. Therefore, the best choice for first-line therapy is a matter of debate and we should choose regimens based on patient characteristics and the toxicity profiles of the regimen. These new regimens are also used to treat patients with locally advanced PC (LAPC) and have yielded promising results in open cohorts or phase II trials. Chemoradiotherapy is also a treatment option for LAPC, but the role of radiotherapy remains controversial. Recently, induction chemotherapy followed by chemoradiotherapy has been recognized as a new promising treatment strategy, and induction chemotherapy with these new effective regimens are also investigated in many clinical trials. Furthermore, it is also important to develop treatment strategies that include second-line treatments, because making all these active cytotoxic agents available to advanced PC patients may improve survival. Ongoing clinical trials are expected to reveal the usefulness of these treatment strategies for unresectable PC patients.

Conversion surgery (CS) is defined as radical pancreatectomy intending R0 resection for patients with initially-unresectable pancreatic cancer who had favorable responses to non-surgical treatment for a certain period. Recently, several articles concerning the effect of CS have been published. Nowadays, CS is recognized as a new therapeutic strategy for unresectable pancreatic cancer. Because of remarkable progress in non-surgical treatment and surgical techniques including those of vascular surgery, it is expected that candidates for CS will increase gradually. However, some patients might develop recurrence at an early stage after CS, and it is important to establish biomarkers for selecting patients for whom CS could be beneficial. In addition, the previous reports of CS were retrospective studies only, and there is no definitive evidence concerning prognostic effects of CS. It is necessary to evaluate the oncological outcomes of CS for patients with unresectable pancreatic cancer by randomized controlled trial.

A 52-year-old male visited our hospital in 2008 after the discovery of pancreatic cysts. CT and MRCP revealed three multilocular cystic lesions throughout the distal pancreas. We diagnosed the patient with branch-duct type intraductal papillary-mucinous neoplasm and continued follow-up every six months. The cystic lesion at the pancreas tail grew gradually at first but has regressed since 2011, based on follow-up by MRCP, leading us to suspect the presence of a mural nodule there within in 2016. Likewise, based on the findings of endoscopic ultrasonography, a mural nodule-like lesion was detected in the cyst. Surgery was deemed necessary and thus we performed a laparoscopic distal pancreatectomy. Histologically, honeycomb-like proliferation of the small cyst was observed in the region considered to be the mural nodule, leading to the diagnosis of a microcystic serous cyst adenoma (SCA). Cases of multiple SCA lesions are rare, particularly those cases in which the solid portion of the lesion consists of microscopic cysts.

Lymphoepithelial cysts (LECs) of the pancreas are rare disease and their characteristics are still poorly understood. A 55-year-old man was referred to our hospital for further examination of a cystic lesion of the pancreas head. The abdominal dynamic CT and MRI revealed an encapsulated cyst which contained two separate components with different enhancement.

Considering the possibility of malignancy, surgical resection was performed. Histological examination of the resected specimen showed that the cyst was lined by squamous epithelium with sebaceous glands, and the cyst wall contained dense lymphoid tissue. Pathological diagnosis was LEC with sebaceous differentiation. LEC of the pancreas are rare, especially those that are accompanied by sebaceous differentiation, and only a few cases have been reported in Japan.

A 55-year-old man was admitted to our hospital with a 2-cm mass in the pancreatic body observed on abdominal US during a medical check-up. Contrast-enhanced CT showed a 2-cm mass in the pancreatic neck that was contrasted more than normal pancreatic parenchyma in the pancreatic phase and had a continuous contrast effect up to the equilibrium phase. EUS showed a hypoechoic oval mass with a well-defined margin, a smooth contour and uniform internal echoes. Contrast-enhanced EUS indicated that the mass showed hyperenhancement compared with the surrounding pancreatic tissue. EUS-FNA was carried out: the cytological diagnosis was acinar cell carcinoma or neuroendocrine tumor, and the histological diagnosis was anaplastic carcinoma. A pylorus-preserving pancreatoduodenectomy was performed. The pancreatic tumor was 16mm in size and covered with a fibrous capsule. Histological examination showed that the tumor cells formed an acinar-like structure and a ductal structure. The tumor cells were immunohistochemically positive for lipase, trypsin and BCL10, and the pathological diagnosis was pancreatic acinar cell carcinoma. Pancreatic acinar cell carcinoma is rarely found in the TS1 stage, but when seeing solid tumors showing expansive growth and enhanced more than invasive ductal carcinoma in the contrast-enhanced CT, it is necessary to consider acinar cell carcinoma.