Case 2 -

Acinar cell cystadenoma (ACA) Dr. Giuseppe Zamboni Universita di Verona

Case History: This 33-year-old female patient presented with a history of abdominal pain. CT of the abdomen revealed an olygocystic lesion in the head of the pancreas, with focal peripheral calcifications. Endoscopic retrograde cholangiopancreatography revealed no communication between the cystic lesion and the ductal system. There was no evidence of cystic fibrosis, von Hippel-Lindau syndrome or polycistic kidney disease. A Whipple resection was performed. The patient is alive and well after 10 years. Case 2 - Figure 1 Click to view with ImageScope Click to view with a Web-Based Viewer Macroscopy: Gross examination of the specimen revealed a well-demarcated multiloculated cyst in the head of the pancreas, measuring 10cm in greatest dimension. The lesion presented a thick, fibrous pseudocapsule, with focal calcifications. The cystic spaces contained clear, pale yellowish fluid and the internal surface was smooth with no solid areas or papillary projections. Neither evident dilatation of the main pancreatic duct nor fibrosis of the pancreatic parenchyma was present. Microscopy: The cystic lesion was characterized by a thick layer of hyalinized connective tissue with focal calcification. The internal surface was lined by heterogeneous epithelium, characterized by either flattened cells resembling normal ductal epithelium or by a single layer of cuboidal cells with the features of acinar cells. These latter cells showed deeply eosinophilic apical granules, with characteristic periodic acid-Schiff-positivity, and basophilic staining at the base of the cell. The nuclei were basally located, uniform and normochromatic with small but evident nucleoli; atypia and mitoses were absent. The cysts were usually connected with small clusters of acinar cells forming acini that opened into the cyst lumen. The surrounding pancreatic parenchyma displayed no specific changes. Immunohistochemistry: The lining cells labeled with antibodies to keratins 8,18,19, and cytokeratin 7, and for acinar markers: trypsin, chymotrypsin and only focally for lipase. This enzyme staining was absent in the flat epithelium and more evident in the pseudoacinar structures budding from the epithelial lining of the cysts. AlphaBamylase was negative. The neuroendocrine markers chromogranin A and synaptophysin were negative. The Ki-67-index was very low:<1%. Diagnosis: Acinar cell cystadenoma (ACA). Differential diagnosis: The differential diagnosis cystic lesions of the pancreas includes cystic formations of differing morphology, pathogenesis and biology. The differential diagnosis from the more common neoplastic cysts, such as serous cystic neoplasms, mucinous cystic neoplasms, intraductal papillary mucinous neoplasms and solid-pseudopapillary neoplasms is usually easy because none of these display acinar differentiation. The differential diagnosis with retention cysts and congenital cysts are based on the exclusive presence of ductal-type epithelial lining in both these lesions. The most important pathological differential diagnosis of ACA is with the cystic variant of acinar cell carcinoma, which have been rarely reported as Aacinar cell cystadenocarcinomas. These neoplasms are frequently large, up to 17cm, and present with multiple cysts. The most important features to be appreciated are the presence of cytological atypia, the frequent mitoses and necrosis. Comments: The acinar cell cystadenoma of the pancreas is a recently recognized type of cystic pancreatic lesion, which is characterized by acinar cell differentiation in the cells lining the cysts, absence of distinct cellular atypia, focal or diffuse involvement of the pancreas and a good prognosis. The knowledge of its existence is important for the differential diagnosis with acinar cell carcinoma. ACA might represent the benign counterpart of the well recognized acinar cell cystadenocarcinoma, but malignant transformation has not been reported. Although the reported cases are still limited, ACA seems to show neither clear age predilection nor preferential localization within the pancreas and only a slight a female predilection. In half of reported cases the cystic lesion caused clinical symptoms such as abdominal discomfort or pain, which led to its surgical resection. In the other patients it was an incidental finding in pancreatic specimens removed because of neoplastic diseases. All the patients resected for the presence of preoperative detected cystic lesion, regardless of whether the lesion was focal or diffuse, are alive and well. Although ACA is rare, it has to be included in the differential diagnosis of cystic lesions of the pancreas. References Albores-Saavedra J. Acinar cystadenoma of the pancreas: a previously undescribed tumor. Ann Diagn Pathol 2002; 6:113-115. Chatelain D, Paye F, Mourra N, Scoazec JY, Baudrimont M, Parc R, Flejou JF. Unilocular acinar cell cystadenoma of the pancreas an unusual acinar cell tumor. Am J Clin Pathol 2002; 118:211-214. Kosmahl M, Pauser U, Peters K, Sipos B, Luttges J, Kremer B, Kloppel G. Cystic neoplasms of the pancreas and tumor-like lesions with cystic features: a review of 418 cases and a classification proposal. Virchows Arch 2004; 445:168-178. Zamboni G, Terris B, Scarpa A, et al. Acinar cell cystadenoma of the pancreas: a new entity? Am J Surg Pathol 2002; 26:698-704.