Huge pseudocyst of the pancreas caused by poorly differentiated invasive ductal adenocarcinoma with osteoclast-like giant cells: report of a case.

A 72-year-old man presented with several week's abdominal distension and jaundice. Under the tentative diagnosis of pancreatic pseudocyst of 22cm in diameter, a percutaneous drainage was performed. Despite the reduction of the pseudocyst, his serum total bilirubin level was increased. At this time, abdominal computed tomography scan showed a tumor at the uncinate process of the pancreas. After the biliary decompression, a total pancreatectomy with the resection of pseudocyst walls and splenectomy was performed. It was histologically proven to be poorly differentiated ductal adenocarcinoma in combination with osteoclast-like giant cells. The pseudocyst was considered to be due to the stenosis of the main pancreatic duct caused by carcinoma of the uncinate process. Five months later, he died of recurrent carcinomatous peritonitis. Osteoclast-like giant cell tumor is a very rare neoplasm, the origin and prognosis of which still remain obscure. However, it has to be considered in the differential diagnosis of cystic changes of the pancreas, especially of pseudocyst. Furthermore, detailed surveys are needed in cases of pseudocyst of the pancreas without chronic pancreatitis, in order to identify small carcinoma of the pancreas.