14 January 2009 – Case of the Week #136
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Case of the Week #136
A 24 year old woman had a 6 cm cystic lesion in the head of the pancreas, which was excised.
What is your diagnosis?
Acinar cell cystadenoma of the pancreas
Acinar cell cystadenoma of the pancreas is a rare benign cystic neoplasm of the pancreas (Pancreas 2008;37:254) that occurs 70% of the time in women (Am J Surg Pathol 2002;26:698). It averages 6 cm in size, and contains unilocular or multilocular cysts containing watery fluid, that are usually not connected with the pancreatic ductal system. Histologically, there are well-circumscribed cystic spaces lined by one or more layers of non-mucinous cuboidal epithelium with abundant eosinophilic, granular and apical cytoplasm and round, basal nuclei. The cells may be arranged as small buds arising from the wall representing abortive acinar formation, but they are not arranged in papillary projections or solid areas. There may be a transition to mucinous ductal epithelium. The cells lack any significant atypia, mitoses or necrosis. No ovarian type stroma is present.
Immunohistochemistry reveals Periodic Acid-Schiff positivity in the lining epithelium as well as staining for pancreatic enzymes (i.e., trypsin-image, chymotrypsin and lipase) as well as cytokeratin 7, although normal cells are CK7 negative. Electron microscopy (image) reveals 200 to 1000 nm dark granules in the apical pole of the lining epithelial cells, rough endoplasmic reticulum and mitochondria (Saenz AJ et al. Acinar cell cystadenoma of the pancreas: Role of Electron Microscopy. USCAP 2008 Abstract, Denver, CO). The granules are consistent with normal exocrine pancreatic zymogen granules.
The differential diagnosis includes pancreatic intraepithelial neoplasia (PanIN) and serous cystadenoma, although both of these lesions lack granular, eosinophilic cytoplasm. It may also resemble acinar cell cystadenocarcinoma, a rare lesion with more complex epithelium, nuclear atypia and prominent nucleoli. These malignant cases may also have necrosis, solid nests of tumor cells, mitotic figures and infiltration into surrounding stroma.
Excision is curative.
1. Volkan Adsay N. Cystic lesions of the pancreas. Mod Pathol 2007;20 Suppl 1:S71
2. Hruban RH, Pitman MB, Klimstra DS. Tumors of the Pancreas. American Registry of Pathology, Armed Forces Institute of Pathology, Washington, DC 2007
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