MALIGNANT INSULINOMA IN A PATIENT WITH TYPE 2 DIABETES MELLITUS

Insulinoma in a patient with pre-existing diabetes mellitus is very rare. We report a case of a malignant insulinoma in a 78-year-old patient with type 2 diabetes mellitus who, after 6 years of insulin treatment, experienced recurrent episodes of hypoglycaemia, with progressive reduction of dosage to cessation. Endogenous hyperinsulinism was confirmed: glucose 35 mg/dt. (74- 106), insulin 23.7 mu U/mL, (7- 17), and negative test for sulphonylureas in the plasma. Endoscopic ultrasonography, magnetic resonance and axial computer tomography identified a non-resectable pancreatic tumour, an infiltrating mesenteric vein, as well as metastatic lesions in the liver. After chemoembolization of metastases, initial reduction of hypoglycemic attacks occurred. A few months later, hypoglycaemia recurred, and combined treatment with somatostatin analogs and diazoxide was employed. Although hypoglycemic agents are the commonest cause of hypoglycemia in type 2 diabetes, insulinomas may occur in these patients. A high degree of suspicion for the presence of an insulinoma should be maintained when unexplained hypoglycemic episodes occur in a patient with previously stable diabetes despite dose adjustment or cessation of the drugs.