We present three cases of newly diagnosed insulinoma at our centre in 2020. AN, a 59yo male, presented with 24 months of intermittent confusion. 72-hour fast confirmed endogenous hyperinsulinaemia, and endoscopic ultrasound and DOTATATE-PET demonstrated a 9mm uncinate process lesion, consistent with an insulinoma. AN underwent Whipple’s surgery, had an uncomplicated recovery, and remains symptom free.
DS, a multi-comorbid 88yo female, was referred with acute dysphasia and hemiparesis, with a glucose level of 2.1mmol. 72-hour fast was positive, and CT pancreas suggested a pancreatic tail insulinoma. DS was medically treated with diazoxide, however dose escalation was limited by fluid retention. Glucocorticoids were commenced, and DS remains stable.
PM, a 74yo male, was referred post syncope with a “LOW” blood glucose, on a background of 2 years of similar episodes. Again, 72 hour fast confirmed endogenous hyperinsulinaemia, and imaging suggested a pancreatic tail lesion. PM underwent distal pancreatectomy, and histopathology revealed a 35mm well differentiated neuroendocrine tumour, with metastatic tumour in 1/1 lymph node.
Insulinomas are rare, with an incidence of 4/1,000,000 per year. 10% are malignant, 10% are ectopic, and 10% are associated with an underlying genetic syndrome. Localisation is vital for treatment planning and prognostication. Structural imaging, with MRI or CT pancreas, can be insufficient, particularly in lesions <10mm. Somatostatin receptor expression in insulinomas is variable, and thus DOTATATE PET imaging can be insensitive. GLP1 receptors (GLP1-R) are highly expressed in insulinomas, and GLP1-R PET imaging presents a novel way of identifying lesions. Malignant insulinomas are larger (>25mm), secrete more insulin, and are almost invariably intra-pancreatic. Treatment is generally debulking surgery, even in metastatic disease. Newer management options include mTOR inhibitors, pasireotide and PRRT. Genetic screening should be considered patients who are young, have hyperparathyroidism, or have recurrent disease.