Ref: Robbins Pathologic Basis of Disease, 8'k edition. & Bailey and Love's Short Practice of Surgery 25th EditionExplanation:INSULINOMAfi-cell tumors (insulinomas) are the MC of pancreatic endocrine neoplasms.They may be responsible for the elaboration of sufficient insulin to induce clinically significant hypoglycemia.The characteristic triad of clinical symptomsHypoglycemia (Glucose levels < 50 mg/dL)CNS manifestations such as confusion, stupor, tremor and loss of consciousnessS ymptoms precipitated by fasting or exercise and are promptly relieved by feeding or glucose administrationClinical featuresProfound hypoglycemia during fasting or after exercise.Signs and symptoms of neuroglycopeniaAnxietyTremorConfusionObtundationSympathetic response (Hunger, Sweating, and Tachycardia)Whipple's triad refers to the clinical criteria for the diagnosis of insulinoma:- Hypoglycemic symptoms during monitored fasting.- Blood glucose levels less than 50 mg/dL. and- Relief of symptoms after administration of intravenous glucose.Factitious hypoglycemia (excess exogenous insulin administration) and postprandial reactive hypoglycemia must be excluded. (Estimation of C peptide will differentiate)In insulinoma, C peptide levels are increased but in Factitious hypoglycemia, it is decreasedMorphologyInsulinomas are most often found within the pancreas and are generally benign.Most are solitary, although multiple tumors may be encountered.Bona fide carcinomas, making up only about 10% of cases, are diagnosed on the basis of local invasion and distant metastases.On rare occasions an insulinoma may arise in ectopic pancreatic tissue.In such cases, electron microscopy reveals the distinctive granules of |3.Solitary tumors are usually small (<2 cm in diameter) and are encapsulated, pale to red- brown nodules located anywhere in the pancreas.Histologically, these benign tumors look remarkably like giant islets, with preservation of the regular cords of monotonous celts and their orientation to the vasculature.Deposition of amyloid in the extracellular tissue is a characteristic feature.ImagingDynamic CT scanning at 5-mm intervals with oral and intravenous contrast is the initial localizing test for insulinoma, with success in 35-85% of cases.Endoscopic ultrasound is also effective but is operator dependentIndium-111 (111 In)-octreotide scintigraphy is less effective (approximately 50%) for localization of insulinoma than other islet cell tumors because insulinomas typically have few somatostatin receptors.Selective arteriography with observation of a tumor "blush'- is the single best diagnostic study for the primary tumor and hepatic metastases. If a tumor is still not identified, regional localization to the head. body, or tail of the pancreas can be accomplished by portal venous sampling for insulin or by calcium angiography.Calcium angiography involves injection of calcium into selectively catheterized pancreatic arteries and measurement of plasma insulin through a catheter positioned in a hepatic vein.TreatmentIt is surgical in nearly all cases.Use of intraoperative ultrasonography greatly facilitates identification of small tumors, especially those located in the pancreatic head or uncinate process.Most insulinomas can be enucleated from surrounding pancreas, although those in the body or tail may require resection.In general, blind pancreatectomy should NOT be performed when the tumor cannot be identified. Approximately 5% of insulinomas are malignant, and 10% are multiple (usually in association with MEN type I).Medical treatment for insulinoma with diazoxide. verapamil, or octreotide has limited effectiveness but may be used in preparation for surgery or for patients unfit for surgery.