Objective : We present a case of insulinoma with a challenging diagnostic scenario.
Methods : A clinical case report.
An 80-year-old-female was transferred to our facility for further evaluation of symptomatic hypoglycemia which was noted during a hospitalization for elective hip replacement. A CT scan of abdomen showed 2.7 cm enhancing mass in the head of pancreas. Retrospectively, patient reported intermittent fasting hypoglycemic symptoms for about 2 years, self-managed with frequent meals. We confirmed biochemical evidence of endogenous hyperinsulinemic hypoglycemia after fasting, with negative sulfonylurea screen. Endoscopic ultrasound again showed pancreatic head mass encasing the gastroduodenal artery plus an additional 6 mm hypoechoic liver lesion. Initial pathology report on endoscopic ultrasound guided-core biopsies was adenocarcinoma of pancreas with metastases to liver. Treatment with diazoxide resolved her hypoglycemia. Due to the incongruence between the pathological diagnosis of adenocarcinoma and her features of insulinoma (hyperinsulinemic hypoglycemia with response to diazoxide, well-circumscribed lesion of pancreas), the case was further evaluated. PET/CT Gallium-68 DOTATATE scan showed pancreatic head mass with intense uptake of Gallium-68 consistent with neuroendocrine tumor (NET), with no abnormal uptake in liver lesion. Pathology slides were re-reviewed with appropriate immunostaining confirming diagnosis of well-differentiated pancreatic NET with extensive stromal fibrosis (which possibly obscured initial diagnosis) and a bile duct adenoma of the liver. Due to location of tumor and her age, she was treated medically with somatostatin analog, Lanreotide, while keeping options open for peptide receptor radionuclide therapy (PRRT) if needed.
Insulinomas are rare functional NETs of pancreas. Diagnosing insulinoma requires high clinical suspicion, laboratory testing for endogenous hyperinsulinemic hypoglycemia during a supervised fast, and various imaging modalities for localization. Surgery is the definitive treatment. Medical management is an option in poor surgical candidates or those with malignant or metastatic insulinomas. In our case, initial clinical picture was more consistent with insulinoma than adenocarcinoma, which prompted re-evaluation ultimately leading to correct diagnosis of insulinoma. Our case highlights potential diagnostic pitfalls and challenges for these rare tumors and importance of close interdisciplinary communication for accurate diagnosis.
Conclusion : When clinical picture is incompatible with a particular diagnosis, clinicians showed always look for alternate diagnosis by utilizing appropriate diagnostic techniques.
Endocrinology Fellow (F2)
University of Iowa Hospitals and Clinics, Iowa City, IA
Iowa City, Iowa
Endocrinology Fellow (F2) at University of Iowa Hospitals and Clinics, Iowa City, IA.
University of Iowa
Staff Physician University of Iowa Hospitals and Clinics