In branch-duct type IPMN the majority of the pancreas is normal in appearance, except for a single or multiple side branches demonstrating marked dilations. These have a cystic mass-like appearance (grape-like cluster), and are located typically in the head/uncinate process. When multifocal, the cystic dilations can be diffused throughout the gland.The main pancreatic duct has a normal diameter (< 4mm in the head and < 3 mm in the tail). The communication between the lesion and the main pancreatic duct on cross-sectional imaging is the key to confirm the diagnosis. 

Branch-duct IPMN are mostly asymptomatic and incidentally diagnosed. Symptoms are present in a minority of patients, and include:

• Aspecific and vague abdominal pain
• Acute pancreatitis
• Jaundice (uncommon)
• Dyspepsia 

The prevalence of malignancy in branch-duct IPMN is much lower (20-25%) than in main-duct/mixed-IPMN. However, the actual rate of progression to malignancy is not well known, because observational cohort studies of patients managed conservatively with long-term follow-up are lacking.

The biologic behavior of branch-duct IPMN seems to be predictable on the basis of symptoms, tumor size, and morphological criteria. The presence of relevant symptoms (jaundice, anorexia, weight loss) and the presence of high-risk stigmata on cross-sectional imaging (enhanced mural nodules) correlates with malignancy. The finding of worrisome features (cyst > 3 cm, non-enhanced mural nodules, thickened cyst walls, dilation of main pancreatic duct) should prompt a careful strict follow-up.

The management of branch-duct IPMN is particularly controversial. The principal effort is towards identifying the group of patients who really benefit of surgical treatment, given the low malignant potential of these lesions and the high morbidity rate of pancreatic resections, even in the long-term (pancreatic exocrine and endocrine insufficiency). In surgical candidates, the choice between a formal resection (pancreaticoduodenectomy, left pancreatectomy) or a parenchyma-sparing operation (middle segment pancreatectomy, enucleation) has to be tailored according to the lesion’s features (location, size, multifocality). Patients should be always informed about the possibility of extending the resection up to a total pancreatectomy, especially when resection margins are positive for malignancy, or in multifocal disease.  

Current management of branch-duct IPMN, according to the International Association of Pancreatology 2012 guidelines, can be summarized as follows:

• Absence of worrisome features at the time of diagnosis: radiologic surveillance on an annual basis
• Presence of worrisome features at the time of diagnosis: radiologic surveillance on a six-month basis
• Presence of high-risk stigmata at the time of diagnosis: surgical resection
• The presence of symptoms attributable to the IPMN (jaundice, weight loss, recurrent acute pancreatitis) generally represents an indication to surgical resection
• In patients initially managed conservatively, the appearance of worrisome features or high-risk stigmata on cross-sectional imaging, the development of symptoms, and the finding on an elevated serum Ca 19.9 represent indications to surgical resection

The majority of branch-duct IPMN is histologically characterized by an gastric-type epithelium. This histological subtype typically gives rise to tubular carcinoma, that displays an aggressive biological behavior, similar to that of pancreatic ductal adenocarcinoma.