Differential Diagnosis

The patient's symptoms of syncopes preceded by blurred vision and profuse diaphoresis, along with hypoglycemia and a pancreatic mass, suggest a diagnosis related to a pancreatic tumor affecting glucose regulation. Here's a categorized differential diagnosis:

• Single most likely diagnosis

  • C. Insulinoma: This is the most likely diagnosis because insulinomas are known to cause hypoglycemia due to excessive insulin production. The symptoms of blurred vision, profuse diaphoresis, and syncopes are consistent with hypoglycemic episodes. Insulinomas are typically pancreatic tumors.

• Other Likely diagnoses

  • A. Glucagonoma: Although glucagonomas usually cause hyperglycemia, a rare presentation could potentially lead to hypoglycemia, especially if there's an imbalance in glucose regulation. However, the primary symptoms and hypoglycemia make this less likely than insulinoma.
  • B. Somatostatinoma: Somatostatinomas can cause hypoglycemia due to the inhibitory effect of somatostatin on insulin secretion being overridden by its effect on reducing glucagon and growth hormone secretion, which can lead to hypoglycemia in some cases. However, this is less common and typically associated with diabetes mellitus due to the inhibitory effect on insulin secretion.

• Do Not Miss

  • Other pancreatic or abdominal tumors: While not directly related to the endocrine function, other tumors could potentially cause hypoglycemia through mechanisms like tumor-related cytokine production (e.g., IGF-1-like factors) or liver metastasis affecting glucose metabolism. Missing a diagnosis of a different pancreatic or abdominal tumor could be critical.
  • Adrenal insufficiency or pheochromocytoma: Although less directly related to the pancreatic mass, these conditions can cause hypoglycemia and significant morbidity if not recognized. Adrenal insufficiency can lead to hypoglycemia, especially under stress, and pheochromocytomas can cause episodic hypoglycemia due to insulin-induced hypoglycemia from excessive catecholamine release.

• Rare diagnoses

  • Mesidioblastosis: A rare condition characterized by an excessive number of pancreatic islet cells, leading to hyperinsulinemic hypoglycemia. It's more common in infants but can occur in adults, often in association with other conditions.
  • Non-islet cell tumor hypoglycemia (NICTH): This condition is caused by non-pancreatic tumors producing IGF-II or other substances that interfere with glucose regulation, leading to hypoglycemia. It's rare and usually associated with large, malignant tumors.