Microcystic serous cystadenoma of the pancreas with subtotal cystic degeneration: another neoplastic mimic of pancreatic pseudocyst.

BACKGROUND: Pancreatic serous cystadenomas are benign cystic neoplasms. Extensive degeneration mimicking a pancreatic pseudocyst has been described in several types of pancreatic neoplasms but has not been documented in serous cystadenomas. We report subtotal cystic degeneration of microcystic serous cystadenomas (MSCA) that produces radiographic, gross, and microscopic overlap with pancreatic pseudocyst.

MATERIALS AND METHODS: Resected MSCA with degenerative change were identified from the pathology archives of Memorial Sloan-Kettering Cancer Center and Johns Hopkins Hospital. The clinical, radiographic, gross, and microscopic findings were reviewed.

RESULTS: Eight MSCAs with subtotal cystic degeneration were retrieved from among 397 resected serous cystadenomas (2.0%). There were 2 men and 6 women (mean age, 52 y). Available radiographic studies showed classic features of MSCA in 2 of 4 cases. Four cysts were unilocular, and 4 were multilocular. Gross features of MSCA were noted focally in the multilocular cases but were not evident in the unilocular examples. The predominant histologic features were those of pancreatic pseudocyst, including a fibrotic cyst wall lacking epithelium and instead composed of myofibroblastic proliferation, hemorrhage, and inflammation. Residual foci of MSCA were embedded in fibrosis, comprising 5% to 60% of the tumor volume.

CONCLUSIONS: Most pancreatic serous cystadenomas display characteristic morphology, including a glycogen-rich epithelial lining and prominent subepithelial capillaries; however, extensive degenerative macrocystic change can obscure these classic features. This phenomenon is to be distinguished from macrocystic serous cystadenoma, in which thin-walled macrocystic spaces are epithelium lined. Thus, serous cystadenoma should be included in the differential diagnosis of pancreatic masses with extensive degenerative cystic change.