Glucagonoma

Definition
Glucagonoma is a rare neuroendocrine tumor (NET) of the pancreas that arises from α‑cells and secretes excessive amounts of glucagon. The hyperglucagonemia produced by the tumor leads to a characteristic clinical picture known as glucagonoma syndrome.

Overview
Glucagonoma belongs to the broader group of pancreatic neuroendocrine neoplasms, which constitute a small proportion of all pancreatic tumors. Most glucagonomas are sporadic and occur in adults, with a median age of diagnosis in the fifth to sixth decade of life. The tumor is usually located in the body or tail of the pancreas, but can arise anywhere within the pancreatic parenchyma. Early identification is challenging because the initial symptoms are often nonspecific; the disease is frequently diagnosed after the development of distinctive cutaneous lesions or metabolic disturbances.

Etymology / Origin
The term combines “glucagon,” the peptide hormone that raises blood glucose levels, with the suffix “‑oma,” derived from the Greek ‑oma (ὄμα), meaning “tumor” or “mass.” Hence, glucagonoma literally denotes a tumor that produces glucagon.

Characteristics

• Clinical Features

  • Necrolytic migratory erythema (NME): A painful, erythematous, and blistering rash that typically begins on the lower abdomen, groin, or perineum and can spread to the limbs. The lesions often have a characteristic “pearls‑plus‑pseudopustules” appearance.
  • Diabetes mellitus: Hyperglycemia results from glucagon‑induced hepatic glucose output and insulin resistance.
  • Weight loss and cachexia: Persistent catabolism and malabsorption contribute to progressive weight loss.
  • Anemia: Often mild to moderate, possibly related to chronic disease and nutritional deficiencies.
  • Thromboembolic events: An increased propensity for venous thromboembolism has been reported.

• Laboratory Findings

  • Serum glucagon levels markedly elevated (often >500 pg/mL, compared with normal <150 pg/mL).
  • Hyperglycemia, hypoalbuminemia, and low zinc levels may be observed.

• Imaging and Diagnosis

  • Cross‑sectional imaging (CT or MRI) typically reveals a hypervascular pancreatic mass.
  • Somatostatin receptor imaging (e.g., ^68Ga‑DOTATATE PET/CT) assists in tumor localization and staging.
  • Histopathology confirms neuroendocrine differentiation, with immunohistochemical positivity for glucagon, synaptophysin, and chromogranin A.

• Treatment

  • Surgical resection: Preferred curative approach for localized disease (e.g., distal pancreatectomy).
  • Medical therapy: Somatostatin analogues (octreotide, lanreotide) can control hormone secretion and tumor growth.
  • Targeted therapy and peptide receptor radionuclide therapy (PRRT): Options for unresectable or metastatic disease.
  • Management of metabolic complications: Glycemic control, nutritional support, and treatment of NME (often responsive to somatostatin analogues).

• Prognosis

  • Prognosis varies with tumor stage; resected localized glucagonomas have relatively favorable outcomes, whereas metastatic disease carries a poorer prognosis. Long‑term surveillance is required due to the potential for recurrence or progression.

Related Topics

• Pancreatic neuroendocrine tumors (PNETs)
• Necrolytic migratory erythema
• Hyperglucagonemia
• Somatostatin analogues
• Peptide receptor radionuclide therapy (PRRT)
• Diabetes mellitus secondary to endocrine tumors

This entry summarizes current, peer‑reviewed medical knowledge about glucagonoma as of the latest available literature.