Pancreatic polypeptide-immunoreactive gallbladder carcinoid tumor.

Gallbladder carcinoid tumor seen in a 62-year-old woman is described. The neoplasm with typical histologic features of classic carcinoid tumor was a 10 x 8 x 3 mm polyp at the neck of the gallbladder. The argyrophilic tumor cells were diffusely immunoreactive for neuron-specific enolase, cystatin C, chromogranin A and pancreatic polypeptide. A few cells were further positive for somatostatin. The presence of neurosecretory-type granules was confirmed ultrastructurally. The clinicopathologic significance of polypoid presentation of gallbladder carcinoid tumor is emphasized.