insulinoma in a patient with type 2 diabetes mellitus.

insulinoma in a patient with pre-existing diabetes is extremely rare. only a small number of cases have been reported all over the world. we report a case of insulinoma in a patient with type 2 diabetes. a 63-year-old female was diagnosed to have diabetes mellitus six years ago, she was given metformin and sulphonylurea to control her glycemia, she had adequate glycemic control for many years, but thereafter, the patient has experienced hypoglycemia after cessation of the treatment since 8 months ago and was hospitalized for further examination, endogenous hypoglycemia was confirmed and the level of serum insulin and c-peptide were elevated. endoscopic ultrasound showed a heterogeneous lesion in the head of the pancreas. head pancreatectomy was done. in the postoperative period diabetes again developed and required oral agents for control.