Whipple's triad is seen in -
Insulinomas are a β cell endocrinal tumour of the pancreas.


The symptoms are produced due to excessive secretion of insulin causing hypoglycemia
Most of the insulinomas are solitary and benign.
Only about 10-15 % of insulinomas are malignant. (Keep in mind that all other endocrine tumours of the pancreas are usually malignant).


Classic diagnostic criteria are Whipple's triad 


Signs and symptoms of hypoglycemia during fasting.
Blood glucose below 2.8 mmol/L (50 mg/dl) during symptomatic episodes.
Relief of symptoms by intravenous administration of Glucose.
Pancreatic carcinoma
Insulinoma
Gastrinoma
Somatostatinoma