A 20-year-old male presented to the Emergency department following a hypoglycaemic seizure. He had a background of ADHD and a recent diagnosis of epilepsy. He was a smoker and consumed 4 standard drinks daily. On examination he was confused with a capillary glucose level of 2.6mmol/L, the confusion improved following intravenous dextrose. The following morning capillary glucose level measured 2.4mmol/L. Electrolytes, liver and renal function were normal and early morning cortisol was 590nmol/L.
A 72 hour fast was commenced and terminated at twelve hours when serum glucose measured 2.1mmol/L, c-peptide 0.9nmol/L (ref 0.1-1.5), insulin level 4mU/L (ref<27mU/L), and proinsulin level 94.4pmol/L (ref <13.3) suggestive of an insulinoma. Insulin antibodies were not detected. CT abdomen revealed a pancreatic tail lesion measuring 36x30x25mm and a left adrenal nodule measuring 33x22mm, 36HU. Biochemical screening confirmed a non-functioning adrenal lesion. The pancreatic lesion exhibited marked DOTATATE activity. He underwent a distal pancreatectomy and left adrenalectomy. Histopathology confirmed a 29mm pancreatic neuroendocrine tumour and a 46mm adrenal cortical neoplasm of uncertain malignant potential. The genetic screening for MEN1, CDKN1B and TP53 were negative. He will continue to have six monthly adrenal MRI and DOTATATE PET for two years and monitoring for biochemical recurrence and screening for primary hyperparathyroidism.
Insulinomas are rare neuroendocrine tumours with an incidence of four cases per million individuals per year (1). Although genetic screening for MEN-1 syndrome was negative, 10-30% of patients have no mutation in the MEN-1 gene (2). Adrenal oncocytic neoplasms (AONs) are extremely rare (3). In a systematic review of 140 cases of AONs 35% were benign, 41% borderline and 24% malignant. The five-year survival being 100%, 88% and 47% respectively (4). Currently there are no standard post-operative surveillance for AONs, however it has been suggested that close follow up for a minimum of five years is required.