The Spectrum of Serous Cystic Tumors of the Pancreas

Abstract

Accurate diagnosis of cystic lesions of the pancreas is important due to their varied clinical course and behavior. Pancreatic cystic neoplasms fall predominantly into two groups: mucinous cystic tumors (MCT) and serous cystic tumors (SCT). While the MCT is a potentially malignant neoplasm that requires resection, the SCT has little or no malignant potential, and therefore should be treated conservatively. SCT of the pancreas is a rare neoplasm. With improvements in imaging methods, the morphologic spectrum and biologic diversity of pancreatic SCTs have broadened in recent years. Currently four subtypes of SCT may be distinguished. The classic and most common type is serous microscopic adenoma. It occurs predominantly in elderly females. It is characterized by a honeycomb-like appearance with a central stellate, occasionally calcified scar. The second type is serous oligocystic adenoma, which exhibits distinctly different macroscopic features from the serous microscopic adenoma. It is composed largely or exclusively of macrocysts (
2 cm), which are few in number. Because the cystic spaces are larger, the imaging appearance of serous oligocystic adenomas may be confused with MCTs, pseudocysts or solitary true cysts. The third type of SCT is solid serous adenoma. This tumor has a solid appearance with well-defined margins. The fourth type is the malignant serous cystadenocarcinoma. Several investigators have reported cases of SCT that are histologically indistinguishable from serous microscopic adenomas, but that show signs of malignancy. The cytological findings of all four types of SCT are similar. SCTs are composed of clear to eosinophilic cuboidal epithelium that is rich in glycogen, as demonstrated by PAS-positive, diastase-sensitive reactivity. The differentiation of SCTs from other cystic lesions is very important because of the great difference in their management. Despite their rarity, recognition of these subtypes of SCT will prevent misinterpretation of the radiologic and macroscopic features of cystic pancreatic lesions.