Insulinoma after sleeve gastrectomy: A case report

Abstract

Background: Laparoscopic sleeve gastrectomy (LSG) has been proposed as an effective and durable treatment for severe obesity and glucose metabolism disorders, and its prevalence has increased from 5% to 37% since 2008. One common complication after bariatric surgery is a postprandial hyperinsulinemic hypoglycemic state. While rare, insulinomas can cause this state, where symptoms are more common in the fasting state; thus, evaluation of insulin secretion is needed. Until now, there have been no reports of insulinoma after LSG.

Case summary: We describe the case of a 43-year-old woman who was referred to the obesity clinic 2 years after LSG was performed. She had symptoms of hypoglycemia predominantly in the fasting state and documented hypoglycemia of less than 30 mg/dL, which are compatible with Whipple's triad. Initially, dumping syndrome was suspected, but after a second low fasting plasma glucose was documented, a 72-h fasting test was performed that tested positive. Computed tomography and endoscopic ultrasound were performed, identifying the presence of a homogeneous hypoechoic semioval tumoral lesion in the pancreas. The diagnosis was compatible with insulinoma. After laparoscopic enucleation of the insulinoma, the symptoms and hypoglycemia disappeared. The histopathological report described a well-differentiated grade 2 neuroendocrine tumor with positive chromogranin and synaptophysin and Ki67 immunopositivity in 4% of the neoplastic cells.

Conclusion: Insulinoma after LSG is a rare condition, and clinicians must be aware of it, especially if the patient has hypoglycemic symptoms during the fasting state.

Keywords: Bariatric surgery; Case report; Glucagon-like peptide 1 amide; Hypoglycemia; Insulinoma; Neuroendocrine tumors.

Figure 1

Imaging examinations. A: Computed tomography image for neuroendocrine tumor. The orange arrow indicates a focal asymmetric reinforcement area of 11 mm × 14 mm of 145 HU in the head of the pancreas; B and C: Endoscopic ultrasound images indicating the presence of a homogeneous hypoechoic semioval tumoral lesion in the pancreas, with well-defined borders measuring 2.1 cm × 1.2 cm, in close apposition to the main pancreatic duct and splenomesenteric confluence without evidence of invasion.

Figure 2

Histology and immunohistochemistry of the tumor. A: Hematoxylin and eosin photomicrograph (40 ×) showing neoplastic cells presenting uniformly round nuclei with granular chromatin (salt and pepper image), typical of neuroendocrine cells with extensive eosinophilic cytoplasm; B and C: Photomicrographs of immunohistochemical staining for chromogranin (B) and synaptophysin (C) (10 ×). Neoplastic cells show strong immunopositivity for both markers in the cytoplasm, which corroborates the neuroendocrine lineage of the neoplasia; D: Immunohistochemical staining for Ki67 (cell proliferation index). Strong nuclear immunopositivity is seen in approximately 4% of neoplastic cells. The tumor was classified as grade 2, according to the 2019 WHO classification.