**Core Concept**
Insulinoma is a rare tumor of the pancreas that produces excess insulin, leading to hypoglycemia. This condition is characterized by the uncontrolled secretion of insulin, resulting in low blood glucose levels.

**Why the Correct Answer is Right**
Insulinoma typically arises from the beta cells of the islets of Langerhans in the pancreas. The tumor produces excess insulin, which binds to insulin receptors on various cells, promoting glucose uptake and glycogen synthesis. This results in a paradoxical increase in glucose uptake and utilization, despite low blood glucose levels. The excess insulin also inhibits the release of glucose from stored glycogen and gluconeogenesis.

**Why Each Wrong Option is Incorrect**
**Option A:** Insulinoma is not typically associated with hyperglycemia, as it is characterized by the excessive production of insulin, which would lower blood glucose levels.
**Option B:** While insulinoma can be caused by genetic mutations, it is not a result of insulin resistance.
**Option C:** Insulinoma is not a type of pancreatic pseudocyst, which is a fluid collection in the pancreas that is not a neoplasm.

**Clinical Pearl / High-Yield Fact**
Insulinoma is often diagnosed with a 72-hour fast, during which symptoms of hypoglycemia are monitored, and blood glucose levels are measured to confirm the diagnosis.

**Correct Answer: D. Insulinoma is a rare tumor of the pancreas that produces excess insulin, leading to hypoglycemia.**