ODP554 insulinoma with a delayed diagnosis of 25 years

Abstract

Abstract Introduction Most insulinomas are rare pancreatic neuroendocrine tumours that are typically sporadic, solitary, with the great majority less than 2cm in diameter at presentation 1; fewer than 5% of insulinomas are larger than 3cm, and in such cases are not infrequently malignant. The median duration of symptoms before diagnosis is variable, but is usually brief, often just 12–18months, although longer durations are occasionally reported. We report the case of a benign insulinoma whose diagnosis was delayed for 25 years, and who eventually presented with a relatively large but benign tumour >4cm in diameter. Case presentation The patient was a50year-old male who presented to our service with a history of hypoglycaemia episodes dating back 25 years. The first, whilst living in Pakistan, he became unwell on his wedding day and was found to have an unspecified but very low blood glucose, confirmed at his local hospital. Since that time, he reported that he had "learned to live with the symptoms" by eating frequent small carbohydrate-rich meals, although missing a meal led to typical hypoglycaemic symptoms. He continued this regimen on moving to the UK, but over a recent period of three months he reported a substantial deterioration in his symptoms(confusion, disorientation, slurred speech, generalised weakness, tachycardia and palpitations), and indeed collapsed on two occasions. He had a fasting glucose of 2.9 mmol/L with grossly elevated and inappropriate insulin and C-peptide level, with a normal cortisol response to Cosyntropin. MRI demonstrated asingle4.1cm lesion in the body of the pancreas, however 68 Gallium-DOTATATE-PET scanning showed no uptake at any site. Accordingly, he was started on diazoxide 50mg tds and referred to the surgical team for distal pancreatectomy: histopathology revealed a 4.4 cm well-differentiated pancreatic neuroendocrine neoplasm of intermediate grade (NET G2, 2017 WHO Pancreatic-NET classification) which immunostained positive for insulin. Post-operatively, his hypoglycaemic episodes have ceased and he remains under active surveillance. Conclusion The great majority of insulinomas are small benign tumours, with a short history, with large tumours often indicating malignancy. Our case demonstrates that untreated and without specific therapy, such tumours may continue to grow and attain a large size without this indicating malignant potential. 68 Gallium-DOTATATE-PET is negative in more than 50% of benign insulinomas. We believe that this represents the longest survival, 25 years, of a patient with a benign insulinoma in the absence of treatment. Presentation: No date and time listed