Adenomatoid tumor of the pancreas: a case report with comparison of histology and aspiration cytology.

We present a 58-year-old woman who presented with a 1.5-cm, hypodense lesion in the head of the pancreas. Endoscopic ultrasound-guided fine-needle aspiration yielded bland, monotonous cells with wispy cytoplasm, slightly granular chromatin, and small nucleoli. A presumptive diagnosis of a neuroendocrine lesion was rendered. Whipple procedure yielded a well-circumscribed, encapsulated lesion with dense, hyalinized stroma and a peripheral rim of lymphocytes. Spindled and epithelioid cells formed short tubules, cords, and nests. The neoplasm stained for CK 5/6, calretinin, vimentin, CD 99, pancytokeratin, and EMA, consistent with mesothelial origin. This characteristic histology and immunohistochemistry is consistent with an adenomatoid tumor. We believe we are the first to report this benign neoplasm in such an unusual location. Herein we address the diagnosis of adenomatoid tumor by histology, immunohistochemistry, and aspiration cytology. Our case is particularly unique in that the histology and cytology are compared and correlated.