**Core Concept**
Tumor lysis syndrome (TLS) is a life-threatening condition that occurs when a large number of cancer cells die rapidly, releasing their contents into the bloodstream. This can lead to a series of electrolyte and metabolic disturbances.

**Why the Correct Answer is Right**
Tumor lysis syndrome is characterized by the release of large amounts of potassium, phosphate, and nucleic acids into the bloodstream, which can lead to hyperkalemia, hyperphosphatemia, and hypocalcemia. The condition is often associated with elevated levels of lactate dehydrogenase (LDH) and uric acid due to the breakdown of nucleic acids.

**Why Each Wrong Option is Incorrect**
**Option A:** Hypernatremia is not typically associated with tumor lysis syndrome, as the condition is more likely to cause hyponatremia due to the release of potassium and phosphate ions.

**Option B:** Hyperuricemia is a common feature of tumor lysis syndrome, as the breakdown of nucleic acids leads to the release of uric acid into the bloodstream.

**Option C:** Hyperkalemia is a hallmark of tumor lysis syndrome, as the release of potassium ions from dying cancer cells can lead to elevated serum potassium levels.

**Clinical Pearl / High-Yield Fact**
Tumor lysis syndrome is often seen in patients with high-grade lymphomas or leukemias, particularly after initiation of chemotherapy or radiation therapy.

**Correct Answer:** A. Hypernatremia