Applied Radiology

Diagnosis

Serous cystadenoma

Findings

Axial contrast-enhanced CT images, axial T2-weighted, T1-weighted pre- and postcontrast magnetic resonance (MR) images (portal venous phase and delayed), and coronal thin-slice magnetic resonance cholangiopancreatography (MRCP) images are provided. Contrast-enhanced CT images demonstrate a large lobulated, low-density mass within the tail of the pancreas. The mass appears to be composed of numerous small cysts, which are not well delineated by CT. The remainder of the pancreas is fatty replaced. MR images demonstrate a T2-hyperintense mass composed of innumerable small cysts. The cyst walls and capsule enhance after the administration of contrast material. A central hypointense scar is present centrally within the mass, which does not enhance on portal venous phase images, but enhances on delayed imaging.

Discussion

Pancreatic serous cystadenomas are uncommon benign cystic neoplasms, which most commonly occur in middle age and elderly patients. As with other cystic neoplasms of the pancreas, there is an increased incidence in females (4:1 ratio of female:male).

Serous cystadenomas account for <1% of all pancreatic tumors and approximately 15% of cystic pancreatic neoplasms. Patients tend to be asymptomatic unless the mass is compressing adjacent structures, such as the common bile duct or duodenum, in which case they may present with jaundice, weight loss, or epigastric abdominal pain/discomfort. Serous cystadenomas may be located in any part of the pancreas, but are most common within the head of the pancreas. Serous cystadenomas vary significantly in size and may measure up to 13 cm, although the average diameter is approximately 5 cm. There is an increased incidence of serous cystadenomas in patients with Von Hippel Lindau (VHL) disease. VHL patients tend to have an earlier age at diagnosis and may have multiple cystadenomas.

Three morphologic patterns of serous cystadenomas have been described: polycystic (70%), honeycomb (20%), and oligocystic (10%). The polycystic morphology consists of innumerable small cysts measuring <2 cm in size, which are separated by fibrous septa which may coalesce into a central scar. The central scar may calcify in some cases. The honeycomb pattern consists of innumerable subcentimeter cysts, which may be indistinguishable by imaging. The honeycomb pattern may also demonstrate a central scar. The oligocystic pattern is the least common and consists of one or more large cysts (>2 cm). The oligocystic pattern may be difficult to differentiate from a mucinous cystadenoma, as there is overlap in morphology. Most commonly oligocystic serous cystadenomas have a lobulated contour, while mucinous cystadenomas tend to have a smoother contour, a feature that may be useful in differentiating the tumors in some cases.

Imaging characteristics vary slightly due to the different morphologies described above. CT may be able to distinguish the cysts, which should demonstrate enhancement of the septa and capsule after the administration of intravenous contrast material. In some cases, the cysts may be too small to differentiate by CT, thereby mimicking a solid neoplasm. As opposed to pancreatic adenocarcinoma, atrophy of the tail of the pancreas is rare, a feature which may be helpful when a honeycomb morphology is present. Approximately 20% to 35% of cases will also have calcifications within the central scar. MR imaging features include hyperintense cysts on T2-weighted images with a hypointense central scar. Generally the cysts are hypointense on T1-weighted images although there is some variability in signal as the cysts may contain small amounts of blood products. As with CT, the septa and capsule usually enhance, while the central scar does not enhance on portal venous phase imaging. Delayed imaging may also be performed which classically shows delayed enhancement of the central scar. Ultrasound imaging characteristics vary depending on the size of the cysts. Larger cysts are usually anechoic with thin walls, while innumerable tiny cysts may appear as an echogenic mass.

Serous cystadenomas, which are adequately characterized by imaging and asymptomatic may be observed with no need for surgery. Imaging features may be correlated with CEA levels measured from cyst aspiration. Carcinoembryonic antigen (CEA) levels are usually normal in serous cystadenomas and elevated in mucinous cystadenomas, although there is some overlap in expected levels. Symptomatic lesions are surgically resected with the surgical approach and extent depending on the location of the lesion.

1. Choi JY, Kim MJ, Lee JY, et al. Typical and atypical manifestations of serous Cystadenoma of the Pancreas: Imaging Findings with Pathologic Correlation. AJR. 2009; 193:136-142.
2. Kim HJ, Lee DH, Ko YT, et al. CT of serous cystadenoma of the pancreas and mimicking masses. AJR Am J Roentgenol. 2008;190 :406-412.
3. Khurana B, Mortelé KJ, Glickman J, et al. Macrocystic serous adenoma of the pancreas: Radiologic-pathologic correlation. AJR Am J Roentgenol. 2003;181:119-123.