Cellular hamartoma resembling gastrointestinal stromal tumor: a solid tumor of the pancreas expressing c-kit (CD117).

Solid tumors of the pancreas are usually neoplastic. We report on two adult patients, each with a solid tumor of the pancreas that presented with an unusual histology and seemed to follow a benign course. The tumors, one located in the body and one in the tail, were well demarcated and composed of irregularly arranged but well-differentiated acini and small intralobular and interlobular ducts embedded in predominantly hypocellular fibrotic tissue that contained fascicles of cytologically bland spindle cells. Islets were lacking, but immunohistochemical staining for chromogranin A and insulin revealed individual scattered insulin-producing cells distributed between acinar and ductal cells. The spindle cell component tissue showed coexpression of CD34, c-kit (CD117) and bcl-2. The follow-up (2 and 4 years) of the patients was uneventful. We propose to designate the tumors as 'cellular hamartoma resembling gastrointestinal stromal tumor.