A Case of a Giant Growing Serous Cystic Neoplasm of the Pancreas
In 2003, during a routine health checkup, a pancreatic cyst measuring 8 cm in diameter was detected in a 51-year-old woman. The cyst was subsequently managed with follow-up care by the previous physician on an outpatient basis. In 2010, the cyst had increased to 12 cm in size and then to 19 cm within approximately the next 6 months. At this time, the patient was referred to our hospital for treatment. At the initial visit, she reported abdominal bloating. However, no medical problems were evident from the patient's health history, and she had no history of pancreatitis, abdominal trauma or alcohol intake. A physical examination showed no sign of anemia in the palpebral conjunctiva or jaundice of the bulbar conjunctiva; the abdomen was soft, flat, and nontender, and no obvious tumor mass was detected by palpation. Blood tests revealed no elevation of pancreatic enzyme levels or tumor markers. Abdominal ultrasonography and contrast-enhanced abdominal computed tomography (CT) scans showed the presence of a partially septated giant cystic lesion measuring 20 × 11 × 13 cm in the abdominal cavity (fig. ). The lining membrane of the cyst was thin, and no solid components or calcifications were noted in the cyst. A beak sign was observed in the pancreas, and the main pancreatic duct in the tail of the pancreas was slightly dilated. Therefore, the mass was considered a cystic tumor of pancreatic origin. On abdominal magnetic resonance imaging, the pancreatic body lesion detected by the CT scan was depicted as high-intensity area on T2-weighted images. These findings were consistent with the characteristics of cystic lesions (fig. ). A septum-like structure was present in the cyst, and dilation was noted in the pancreatic duct in the tail of the pancreas. Endoscopic ultrasonography showed extramural compression of the middle part of the gastric body. Although imaging studies of the same site could not reveal the entire extent of the cyst because of its enormous size, the cyst demonstrated low-level internal echoes and did not show any obvious solid component. A septum-like structure was observed, but there was no microcystic lesion with a characteristic honeycomb pattern. Endoscopic retrograde cholangiopancreatography displayed only the main pancreatic duct in the head of the pancreas; the cyst compressed the tail side. Based on these findings, the differential diagnosis included serous cystic neoplasm (SCN), mucinous cystic neoplasm, and branch duct-type intraductal papillary mucinous neoplasm in the neoplastic category as well as pancreatic pseudocyst in the nonneoplastic category. Because this mass was increasing in size and abdominal bloating was present, surgical resection was deemed appropriate. Therefore, a distal pancreatectomy with splenectomy was performed. The cystic content was serous fluid of a dark, muddy color, suggesting previous bleeding (fig. ). On histopathological examination, the lining membrane had a papillary structure composed of cuboidal cells with round nuclei. The cells stained PAS-positive and diastase PAS-negative, thus indicating the presence of glycogen (fig. ). These findings led to the definitive diagnosis of SCN.