Pancreatic resections are inevitably invasive due to anatomical, physiological and pathological features of the pancreas. To reduce the level of invasiveness, surgeons have attempted to reduce the loss of pancreatic parenchyma and preserve adjacent structures such as the duodenum and spleen. In the West, laparoscopic pancreatic resections have been performed since the 1990's and robot-assisted laparoscopic pancreatic resections have been attempted since 2000. However, in Japan, laparoscopic distal pancreatectomy was approved for reimbursement by national insurance in 2012 and robot-assisted laparoscopic pancreatic resections were approved in 2020. While our predecessors pioneered the development of minimally invasive pancreatic resections, we have been outdone by the rest of the world partly due to the late approval of laparoscopic pancreatic resections by the national insurance system. Nevertheless, we can disseminate minimally invasive pancreatic resection safely and widely throughout the country by enhancing the surgical education system. It is urgently needed to provide front-line surgeons with systematic education for robot-assisted surgery.

Robotic-assisted surgery is expected to be a technology that enables precise, safe, and minimally invasive surgery with its magnified stereoscopic visualization and multi-joint function. In distal pancreatectomy especially, the superiority of minimally invasive surgery over laparotomy in short-term outcomes has been demonstrated with a high level of evidence, and robotic-assisted surgery is expected to improve long-term outcomes through precision and avoiding laparotomy, as well as to expand its application to patients who have difficulty with laparoscopic surgery. However, pancreaticoduodenectomy has a probable advantage in reconstructive procedures compared to laparoscopic surgery, and evidence is now accumulating. As the treatment of advanced pancreatic cancer is undergoing a major shift toward multidisciplinary treatment with potent systemic chemotherapy, total neoadjuvant therapy, and pancreatic resection, sophisticated and minimally invasive robotic-assisted surgery is expected to be highly compatible with these strategies. In the future, clinical studies with a high level of evidence, including randomized controlled trials, are needed to verify the long-term oncologic outcomes.

Minimally invasive surgery has emerged as an alternative to open surgery, and this approach has also been applied to pancreatectomy. With the increase in the number of minimally invasive pancreatic resections (MIPR), several studies comparing MIPR and conventional open pancreatectomy have been reported. In addition, with the application of robotic-assisted pancreatectomy, the number of studies comparing robotic-assisted pancreatectomy and laparoscopic pancreatectomy has also increased. In Japan, laparoscopic pancreatectomy, such as laparoscopic distal pancreatectomy or pancreatoduodenectomy has been covered by national health insurance for patients with benign to low-grade malignancies. The indication for this procedure was then expanded to patients with malignancies. In Japan, MIPR is covered by insurance for patients with both benign and malignant diseases. However, during the introductory period, the indications should be limited to patients with benign to low-grade malignancies. In this review, we aimed to provide a comprehensive overview of the current status of MIPR, especially for patients with benign to low-grade malignancies.

Since minimally invasive pancreatectomy requires advanced surgical techniques, it is important to assure safety during the learning curve. In 2016, laparoscopic distal pancreatectomy was covered by insurance for patients with pancreatic cancer. In 2020 laparoscopic and robot-assisted pancreaticoduodenectomy with lymph node dissection were also covered by national insurance. The most effective treatment for pancreatic cancer is surgical resection, although pancreatic cancer has an overall poor prognosis. In the surgical treatment of patients with pancreatic cancer, preoperative and postoperative adjuvant treatments are extremely important to improve the prognosis. Minimally invasive pancreatectomy is expected to be associated with early postoperative recovery. Laparoscopic surgery allows delicate dissection by facilitating recognition of detailed anatomy with high resolution imaging. Traditionally, Japanese surgeons have performed safe and curative surgery by understanding the anatomical structures. The development of novel approaches to minimally invasive pancreatectomy with precise understanding of anatomy is expected in the future.

A 75-year-old woman was referred with a two-month history of appetite loss. Computed tomography scans revealed a 35mm tumor in the pancreatic tail and a 10mm round tumor in the right lung. Upper gastrointestinal endoscopy was unremarkable. Endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) of the pancreatic tumor was performed. Histologically, the tumor was diagnosed as a poorly differentiated adenocarcinoma with a signet ring cell component. Due to the patient's inability to maintain her nutritional status, we decided that systemic chemotherapy was not indicated. Seven days after EUS-FNA, the patient was discharged and she died 113 days later.

A 40-year-old woman underwent infertility treatment for one year. She developed left upper quadrant abdominal pain and distention over the previous several months and presented with worsening symptoms. A left upper quadrant abdominal mass was found on physical examination and a cystic tumor imaged by ultrasonography. She was transferred for further evaluation. Abdominal computed tomography scan and magnetic resonance imaging revealed a 16cm multi-cystic tumor in the left upper quadrant. There was no dilatation of the main pancreatic duct or communication between the tumor and the main pancreatic duct. The tumor was diagnosed as a mucinous cystic neoplasm (MCN) of the pancreatic body and tail. A distal pancreatectomy with splenectomy was performed and she was discharged on postoperative day 13 without complications. Pathological diagnosis was a mucinous cystic neoplasm with intermediate grade dysplasia in the pancreatic tail. The tumor had ovarian-type stroma positive for estrogen and progesterone receptors. Several patients with MCN diagnosed during pregnancy have been reported. A relationship between the tumor and ovarian hormones has been suggested, but there are no reports of MCN diagnosed during infertility treatment. We present a case report with literature review of the relationship between MCN, pregnancy and infertility treatment.

A 50-year-old woman with back pain who was followed for schizophrenia and obesity was admitted to the hospital. Abdominal computed tomography (CT) scan revealed a 25mm tumor in the pancreatic head. Contrast-enhanced magnetic resonance imaging (MRI) in the arterial phase showed a ring-like enhancing tumor with a hypovascular area in the central portion. Positron emission tomography-CT scan showed the tumor with a maximal standardized uptake value of 8.61. Carbohydrate antigen 19-9 level was elevated to 40U/ml. We diagnosed this lesion as a nonfunctional pancreatic neuroendocrine neoplasm or pancreatic ductal adenocarcinoma and performed a subtotal stomach-preserving pancreaticoduodenectomy. Histopathological findings revealed a pancreatic neuroendocrine neoplasm, with atypical cells in the enhanced area and fibrosis in the hypovascular area as seen on the contrast-enhanced MRI in the arterial phase. We report a patient with a rare neuroendocrine neoplasm with a ring-like enhancing pattern.

A 15-year-old male was found to have a posterior mediastinal tumor and low-attenuation mass in the pancreatic head on computed tomography (CT) scan. The masses did not enhance between the arterial and venous phases. A hypoechoic mass was seen in the pancreas on endoscopic ultrasound (EUS) and EUS-guided fine needle biopsy (EUS-FNB) using a Franseen needle was performed. The biopsy specimen contained a proliferation of spindle-shaped cells with scattered mature ganglion cells. Immunocytochemistry showed positive staining with S-100 protein in spindle-shaped cells and with synaptophysin in ganglion cells. CT scan guided needle biopsy of the posterior mediastinal tumor was performed and the same histological and immunocytochemical findings obtained. The definitive diagnosis was a pancreatic ganglioneuroma (GN) and posterior mediastinal GN and he underwent a follow-up examination. GN is a rare benign soft tissue tumor that arises from sympathetic nerve fibers, frequently discovered during childhood or in young adults and pancreatic GN are exceedingly rare. This is the first case report of a pancreatic GN diagnosed by EUS-FNB based on our literature search. Recently, an EUS-FNB needle was developed with improved core tissue procurement, allowing for immunohistochemistry required for diagnosis. EUS-FNB may be useful for evaluation of an unusual pancreatic mass such as in the present patient.