Perren et al.[17] reported that neurofibromin expression was negative in an insulinoma of the pancreas in a patient with NF-1, but that neurofibromin expression was strongly positive in a sporadic insulinoma on immunohistochemistry; in addition, neurofibromin expression was reduced at the mRNA level in the insulinoma of the pancreas in a patient with NF-1. The gene discussed is NF1; the disease is pancreatic insulinoma.