OBJECTIVE To review the features of patients with benign and malignant cystadenomas of the pancreas, focusing on preoperative diagnostic accuracy and long-term outcome, especially for nonoperated serous cystadenomas and resected cystadenocarcinomas. BACKGROUND Serous cystadenomas (SCAs) are benign tumors. Mucinous cystic neoplasms should be resected because of the risk of malignant progression. A correct preoperative diagnosis of tumor type is based on morphologic criteria. Despite the high quality of recent imaging procedures, the diagnosis frequently remains uncertain. Invasive investigations such as endosonography and diagnostic aspiration of cystic fluid may be helpful, but their assessment is limited to small series. The management of typical SCA may require resection or observation. Survival after pancreatic resection seems better for cystadenocarcinomas (MCACs) than for ductal adenocarcinomas of the pancreas. METHODS Three hundred ninety-eight cases of cystadenomas of the pancreas were collected between 1984 and 1996 in 73 institutions of the French Surgical Association. Clinical presentation, radiologic evaluation, and surgical procedures were analyzed for 144 operated SCAs, 150 mucinous cystadenomas (MCAs), and 78 MCACs. The outcome of 372 operated patients and 26 nonoperated patients with SCA was analyzed. RESULTS Cystadenomas represented 76% of all primary pancreatic cystic tumors (398/522). An asymptomatic tumor was discovered in 32% of patients with SCA, 26% of those with MCA, and 13% of those with MCAC. The tumor was located in the head or uncinate process of the pancreas in 38% of those with SCA, 27% of those with MCA, and 49% of those with MCAC. A communication between the cyst and pancreatic duct was discovered in 0.6% of those with SCA, 6% of those with MCA, and 10% of those with MCAC. The main investigations were ultrasonography and computed tomography (94% for SCA, MCA, and MCAC), endosonography (34%, 28%, and 22% for SCA, MCA, and MCAC respectively), endoscopic retrograde cholangiopancreatography (16%, 14%, 22%), and cyst fluid analysis (22%, 31%, 35%). An accurate preoperative diagnosis of tumor type was proposed for 20% of those with SCA (144 cases), 30% of those with MCA, and 29% of those with MCAC. An atypical unilocular macrocyst was observed in 10% of SCA cases. The most common misdiagnosis for mucinous cystic tumors was pseudocyst (9% of MCAs, 15% of MCACs). Intraoperative frozen sections (126 cases) allowed a diagnosis according to definitive histologic examination in 50% of those with SCA and MCA and 62% of those with MCAC. For management, 93% of patients underwent surgery. Nonoperated patients (7%) had exclusively typical SCA. A complete cyst excision was performed in 94% of benign cystadenomas, with an operative mortality rate of 2% for SCA and 1.4% for MCA. Resection was possible in 74% of cases of MCAC. Mean follow-up of 26 patients with nonresected SCAs was 38 months, and no patients required surgery. For resected MCACs, the actuarial 5-year survival rate was 63%. CONCLUSIONS Spiral computed tomography is the examination of choice for a correct prediction of tumor type. Endosonography may be useful to detect the morphologic criteria of small tumors. Diagnostic aspiration of the cyst allows differentiation of the macrocystic form of SCA (10% of cases) and the unilocular type of mucinous cystic neoplasm from a pseudocyst. Surgical resection should be performed for symptomatic SCAs, all mucinous cystic neoplasms, and cystic tumors that are not clearly defined. Conservative management is wholly justified for a well-documented SCA with no symptoms. An extensive resection is warranted for MCAC because the 5-year survival rate may exceed 60%.