A 24 year old gentleman presented following an episode where he became sleepy and disorientated whilst driving and had to pull over. He was confused and lethargic and paramedics found blood glucose of 2 mmol/l. He gave a 3-week history of extreme lethargy, nausea, epigastric discomfort, blurring of vision and constant hunger. He denied recent weight changes and had no significant past medical/family history. Biochemical evaluation was as follows; Laboratory glucose 1.4 mmol/l, C-peptide 404 pmol/l, insulin 7.7 mU/l, Cortisol 430 nmol/l, Ca199 6 IU/ml, TSH 0.57 mU/l, IGF-1 25 nmol/l. MRI pancreas was performed which revealed multiple metastases throughout the liver but no primary lesion identified due to severe motion artefact. Subsequently a full staging CT CAP was performed which revealed pancreatic duct dilatation with a possible obstructing primary lesion at the pancreatic body/tail junction, with liver metastasis. The radiologist confirmed possible metastatic insulinoma or neuroendocrine tumour and this was discussed at the upper GI MDT meeting. Meanwhile, he was commenced on diazoxide at a dose of 100 mg TDS with good response. He proceeded to have a liver biopsy and Octreotide scan. The histology from liver biopsy revealed grade 2 neuroendocrine tumour, metastasize to the liver in keeping with a pancreatic primary neuroendocrine tumour (clinically insulin producing) with Ki67 of 13%. Octreotide scan revealed highly avid segment 7 liver lesions but interestingly other lesions including the pancreatic lesion were octreotide negative indicating variation in disease, hence PET scan was organised. The initial management is chemotherapy with Streptozocin and Capecitabine with surgery/embolization as required to treat residual disease.
Conclusion: Malignant insulinoma is rare accounting for only 512% of cases of insulinoma with median survival of approximately 2 years. This case highlights the challenges of insulinoma diagnosis and localisation and the role of first line medical therapy as opposed to surgery in those with unresectable metastasis.