Pancreatic insulinoma combined with glucagon positive cell: A case report

Abstract

We present a 70-year-old man who was referred for surgery with uncontrollable hypoglycemia. Ultrasonography and abdominal contrast computed tomography revealed a hypervascular tumor of 1 cm in diameter in the pancreatic tail. With a diagnosis of insulinoma, we performed a distal pancreatectomy. The patient showed a good postoperative course without any complications. The patient's early morning fasting hypoglycemia disappeared. The respective levels of C-peptide and insulin dropped from 14.9 ng/mL and 4860 μIU/mL preoperatively to 5.3 ng/mL and 553 μIU/mL after surgery. A histopathological examination demonstrated that the tumor was a pancreatic neuroendocrine tumor, grade 1. Immunostaining was negative for insulin and positive for CD56, chromogranin A, synaptophysin and glucagon. These findings suggested that the tumor was clinically an insulinoma but histopathologically a glucagonoma. Among all insulinoma cases reported between 1985 and 2010, only 5 cases were associated with independent glucagonoma. In this report, we characterize and discuss this rare type of insulinoma by describing the case we experienced in detail.

Keywords: Glucagon; Hypoglycemia; Insulinoma; Neuroendocrine tumor; Pancreas.

Figure 1

Removal of tumor. A: Enhanced abdominal computed tomography showed a tumor of 1 centimeter in diameter in the tail of the pancreas which was highly contrasted in the arterial phase (arrow); B: Endoscopic ultrasonography identified a uniformly hypoechoic tumor which measured 11 mm × 6 mm with a smooth surface in the tail of the pancreas; C: The resected specimen obtained from distal pancreatectomy and splenectomy included a solid whitish nodule (arrow).

Figure 2

Immunostaining histological findings for the main lesion and the microadenoma (× 100). A: The main lesion revealed positive for glucagon; B: The main lesion revealed negative for insulin; C: The microadenoma revealed most positive for glucagon; D: The microadenoma revealed weakly positive for insulin.