Functioning gangliocytic paraganglioma of the ampulla: clinicopathological correlations and cytologic features.

Gangliocytic paraganglioma (GP) is a rare neuroendocrine tumor almost exclusively found in the ampulla. It is considered nonfunctioning in the literature. We herein report the first case of functioning GP arising in the ampulla. Our patient had a constellation of ampullary neuroendocrine tumor, flushing, diarrhea, weight loss, diabetes mellitus, and cholelithiasis, consistent with effects of serotonin and somatostatin that were overexpressed by the ampullary neuroendocrine tumor. The serum serotonin level was elevated. Immunostaining confirmed somatostatin expression by the epithelioid cells and ganglion-like cells of GP. After surgical resection of the tumor, the patient became euglycemic. However, computed tomography (CT) scan 3 months post-surgery showed regional lymphadenopathy suspicious for residual/recurrent/metastatic disease. In the interim, his flushing and hyperglycemia recurred and worsened. Increased awareness about the functioning potential of GP is important so that the underlying pathophysiologic link is not overlooked and patients are appropriately managed. Moreover, we describe the cytologic features that help make the preoperative diagnosis, and these have not been previously described.