Abstract

A 70-year-old man with asymptomatic cystic nodules in the hepatoduodenal ligament, observed during routine ultrasonographic investigation, was referred to our hospital. Contrast-enhanced computed tomography (Fig. 1a), and three-dimensional images constructed using SYNAPSE VINCENT (Fig. 1b) revealed the compression of the left portal vein and a solid component (magenta) by the upper end of the cystic nodules. The serial cystic component in the hepatoduodenal ligament was suspected of communicating with a branched-type intraductal papillary mucinous neoplasm (IPMN; white arrowhead) by magnetic resonance imaging (MRI) (Fig. 1c). Endoscopic ultrasonography showed that the upper end of the cystic wall was thickened and showed contrast (Fig. 2a). Positron emission tomography suggested mild accumulation at the thickened cystic wall and branched-type of IPMN (Fig. 2b). The tumor markers related with pancreatic duct adenocarcinoma were not elevated. Because of the possibility of malignancy, pancreatoduodenectomy was performed, which revealed that the cystic tumor was tightly adhered to the adjacent tissues. Macroscopically, the cystic lesion was observed to communicate with the pancreas, and pathological examination revealed that the cysts lacked an endothelium and were accompanied by inflammatory cells, without malignancy. A biochemical analysis of the cystic fluid showed a high amylase level of up to 11 300 U/mL. Collectively, the extrapancreatic serial cysts were pseudocysts caused by the ruptured IPMN, which had gradually increased in size. The patient was discharged 3 weeks after the operation, without any complications. This case raised two clinical questions. First, what type of cystic tumor was present in the hepatoduodenal ligament? Since patient showed no symptoms, it was not easy to determine if curative resection should be performed. The tumor seemed to increase in size based on an annual ultrasonographic investigation. Fine needle aspiration of the content of the cystic tumor was avoided, because the fluidic component might scatter in the abdominal cavity. The communication indicated by MRI between the cystic tumor in the hepatoduodenal ligament and IPMN was not a confident finding. Second, if we could reach the diagnosis of ruptured IPMN before surgery, what would the optimal treatment be for this case? The cystic size, which is one of the criteria in determining the malignant potential of branched type IPMN, is not a worthy evaluation, because intracystic component was already split out as an extrapancreatic pseudocyst and was increasing in size. Based on this clinical situation, we considered that the extirpation of the extrapancreatic pseudocyst as well as intrapancreatic IPMN might be the optimal treatment for this patient. There have been two case reports of ruptured IPMN as far as we investigated. The first case report described two cases. A 55-year-old man had intraductal papillary mucinous adenocarcinoma (IPMC), of which the mucinous component ruptured out into the peritoneal cavity,1 and a 68-year-old man had IPMC forming gastric and duodenum fistulas. The other report showed that an 80-year-old man had intraductal papillary mucinous adenoma (IPMA) forming femur fistulas.2 Thus, IPMN, including the current case, could rarely exhibit an atypical clinical course requiring invasive treatment with substantial physical stress, even though the tumor was not histologically malignant. This rare feature of IPMN should be taken in to account during observation.