P023 and OC3
Hard-to-find Insulinomas: Is there a role for GLP-1 receptor scintigraphy?
A Theodoraki, D Wild, S Perera, T Kurzawinski, J Bomanji, PM Bouloux, B Khoo
In May 2009 a 55 year old primary school teacher presented with light-headedness, confusion and collapses, that were prevented by eating. During one of these episodes she was noted to have a low blood glucose. She underwent a 24hour supervised fast during which she became hypoglycaemic with a plasma glucose of 1.7 mmol/L, inappropriately high insulin level at 9.0 mU/L and a raised C-peptide at 834 pmol/L. Sulphonylurea screen was negative.
From her previous medical history she was known to be hypertensive, in June 2008 she had had a left pneumonectomy for a salivary gland-type lung tumour and in May 2008 was diagnosed with a cerebellar ependymoma.
To investigate the endogenous hyperinsulinaemic hypoglycaemia further she had a CT abdominal scan followed by MRI and abdominal US, that all failed to reveal a lesion in the pancreas and showed a liver lesion with features suggestive of a haemangioma. On endoscopic US the pancreas appeared normal and a node superior to the pancreas was identified. Somatostatin receptor imaging with 111InPentetreotide was negative.
Somatostatin receptor imaging with 68Gallium DOTATATE PET CT and 111In-DTPA Exendin-4 SPECT/CT scans were performed which showed a lesion in the tail of the pancreas and a lymph node. An intra-arterial calcium stimulation test with selective angiography showed increased insulin secretion from the territory supplied by the splenic artery. This confirmed the presence of an insulinoma in the tail of the pancreas, consistent with 68Ga-DOTATATE PET/CT and 111In-DTPA Exendin-4 SPECT/CT.
The patient underwent enucleation of the insulinoma. During the operation a hard lobulated liver lesion was identified and the excised. On histology the sections from the pancreas showed a well differentiated insulinoma. The lymph node in the tail of the pancreas on histology had reactive features only and the liver lesion proved to be metastasis from the salivary gland-type lung tumour.
Insulinomas can be difficult to image preoperatively. Glucagon Like Peptide-1 (GLP-1) receptors are expressed in beta cells and GLP-1 receptor scintigraphy seems to be a reliable, non invasive way to image insulinomas.