Clinical and diagnostic aspects of cystic insulinoma.

Cystic endocrine tumors of the pancreas rarely occur, and only a few cases of cystic insulinoma have been reported to date. Diagnosis of insulinoma could be difficult if the functional activity is incomplete, possibly leading to blunted symptoms of hypoglycemia and failure in the laboratory to provide evidence of hyperinsulinemia. We report a clinical case of cystic insulinoma confirmed by histological examination after surgery, characterized by a high intracystic insulin concentration despite normal blood basal levels of the hormone. New diagnostic findings from dynamic tests and cystic fluid examination have been carefully focused on.