A rare case of insulinoma presenting with deep vein thrombosis, successfully treated with minimally invasive procedures including microwave ablation

SUMMARY: Treatment of insulinoma can be challenging, while surgical resection is considered the first line. When surgery is contraindicated or is refused, minimally invasive procedures such as selective arterial embolization, local ablative techniques including alcohol ablation, radiofrequency ablation and microwave ablation are being used of late. The world’s first microwave ablation of insulinoma was performed in 2015, after which there have been only a handful of reported cases. A 78-year-old female presented with painful swelling of the left lower limb. She was drowsy and was previously misdiagnosed as epilepsy when she had similar episodes since 2 years ago. She had hypoglycaemia with high serum insulin and C-peptide, and mildly high adjusted calcium, serum prolactin. MRI did not show pituitary adenoma. Lower limb venous duplex scan showed left lower limb deep vein thrombosis for which she was treated with anticoagulation. CT of the abdomen showed a tumour measuring 1.8 cm, located in the antero-superior aspect of the body of the pancreas, with the superior surface being abutted by the splenic artery and the inferior surface being 3 mm above the pancreatic duct, suggestive of an insulinoma. Selective transcatheter arterial embolization of the pancreatic tumour was attempted but was abandoned due to multiple small feeding arteries. Microwave ablation of the tumour was performed successfully. Since there was a possibility of the ablation being compromised due to the heat sink at the splenic artery, 2 mL of 99% alcohol was injected into the rim of the tumour near the artery. She was subsequently normoglycaemic. She defaulted follow up for repeat imaging of pancreas and screening for MEN1 syndrome due to the impact of the COVID-19 pandemic. Minimally invasive procedures are preferred over surgery in selected patients with insulinoma, out of which microwave ablation could be preferentially recommended due to its efficacy and minimal complications. We report the first case of MWA performed in combination with AA in successfully treating insulinoma to our knowledge. This is also the first reported case of DVT associated with isolated insulinoma prior to intervention, though it is rarely reported in MEN1 syndrome. LEARNING POINTS: Novel therapeutic minimally invasive procedures are successful in treating selected cases of insulinoma. Microwave ablation could be recommended preferentially over selective trans-arterial embolization, and radiofrequency ablation in treating insulinoma due to its efficacy and minimal complications. We report the first case of microwave ablation performed in combination with alcohol ablation in successfully treating insulinoma to our knowledge.