Cystic Pancreatic Neoplasms
Serous Cystadenoma (Microcystic/Macrocystic Serous Cystadenoma) Serous cystadenoma is a benign neoplasm characterized by numerous tiny serous fluid-filled cysts.
This tumor frequently occurs in older patients and has an increased association with von Hippel-Lindau disease.
Tumors range in size from 1 to 12 cm, with an average diameter at presentation of 5 cm. T2-weighted images reveal small cysts and intervening septations as a cluster of small grape-like high-signal-intensity cysts with a central scar.
Cystic pancreatic masses that contain cysts measuring less than 1 cm in diameter may represent microcystic cystadenoma or side-branch type intraductal papillary mucinous tumor (IPMT), which can be difficult to distinguish.
Definition of communication with the pancreatic duct on MRCP images establishes the diagnosis of side branch IPMT. Uncommonly serous cystadenomas may be microcystic (cysts measuring from 1–8 cm) oligo- or unilocular (Friedman et al. 1983; Martin and Semelka 2000).
Microcystic and macrocystic serous tumors represent morphologic variants of the same benign pancreatic neoplasm, namely serous cystadenoma. Relatively thin uniform septations and absence of infiltration of adjacent organs and structures are features that distinguish serous cystadenoma from serous cystadenocarcinoma. Tumor septations usually enhance minimally with gadolinium on early and late post-contrast images, although moderate enhancement on early post-contrast images may occur. Delayed enhancement of the central scar may occasionally be observed, and is more typical of large tumors.
Serous Cystadenocarcinoma (Microcystic Serous Cystadenocarcinoma) malignant pancreatic tumor is extremely rare. Distinction from benign serous cystadenoma is difficult on histologic grounds alone and may only be established by the presence of metastatic disease or local invasion.
Mucinous cystic neoplasms of the pancreas are characterized by the formation of large unilocular or multilocular cysts filled with abundant, thick, gelatinous mucin. Mucinous cystic neoplasms should be interpreted as mucinous cystadenocarcinomas of low-grade malignant potential in order to reinforce the need for complete surgical resection and close clinical follow up. Mucinous cystic neoplasms occur more frequently in females (6 to 1) and approximately 50% occur in patients between the ages of 40 and 60 years. These tumors usually are located in the body and tail of the pancreas. They may be large (mean diameter of 10 cm), multiloculated, and encapsulated. There is a great propensity for invasion of local organs and tissues (Martin and Semelka 2000).
On gadolinium-enhanced T1-weighted fat-suppressed images, large, irregular cystic spaces separated by thick septa are demonstrated. Mucinous cystadenomas are well circumscribed and they show no evidence of metastases or invasion of adjacent tissues. Mucinous cystadenomas described pathologically as having borderline malignant potential, may be very large, but may not show imaging or gross evidence of metastases or local invasion. Mucin produced by these tumors may result in high signal intensity on T1- and T2-weighted images of the primary tumor and liver metastases (Martin and Semelka 2000).