Asymptomatic insulinoma: a case report and autopsy series

We investigated the prevalence and characterization of asymptomatic pancreatic tumors in response to our experience of asymptomatic insulinoma.

A patient with a moderately low glucose level and pancreatic incidentaloma detected by CT was examined. Pancreas specimens from 423 autopsy cases were also pathologically examined systematically by hematoxylin-eosin staining.

The examined patient showed no profile characteristic of insulinoma by fasting or loading tests, however, ASVS led to diagnosis of insulin-producing tumor. The tumor was resected with the pancreatic body and tail and revealed to be 10 mm in diameter, with 98.5% of the cells positive for insulin. Pathological evaluation confirmed a well-differentiated endocrine pancreatic tumor, which was suggestive of an incidentally detected asymptomatic insulinoma. Microscopic evaluations of pancreatic specimens from 423 autopsy cases revealed pancreatic monotonous lesions in 6 cases (1.42%). In 4 autopsy specimens large enough for immuno-histochemical evaluation, the lesions were positive for glucagon but negative for insulin.

As concerns the present study, retrospective immunohistochemical investigation in autopsy cases revealed the presence of asymptomatic glucagonoma but no asymptomatic insulinoma. Advances in diagnostic imaging, however, might raise the probability of detecting early asymptomatic stages of insulinoma incidentally. ASVS appears to be sensitive even for asymptomatic incidental insulinomas.