Intrapancreatic accessory spleen: mimic of pancreatic endocrine tumor diagnosed by endoscopic ultrasound-guided fine-needle aspiration biopsy.

Intrapancreatic accessory spleen forms a well-defined nodule within the tail of the pancreas and is commonly mistaken by imaging studies as a neuroendocrine tumor. We report three cases of intrapancreatic accessory spleen diagnosed by endoscopic ultrasound (EUS)-guided fine-needle aspiration (FNA) biopsy. Imaging studies showed well-circumscribed nodules in the tail of the pancreas. Two lesions were clinically suspicious for pancreatic neuroendocrine tumors and one appeared to be a cyst. EUS-guided FNA revealed predominantly small lymphocytes with a subset of histiocytes, conspicuous eosinophils, and plasma cells. There was also characteristic CD8 positive immunostaining of endothelial cells in cell block sections. We report the first series of accessory spleen in the pancreas diagnosed by EUS-guided FNA with the aid of CD8 immunostaining of splenic sinus endothelial cells. (c) 2008 Wiley-Liss, Inc.