**Core Concept**
Tumor lysis syndrome (TLS) is a life-threatening metabolic disorder that occurs when a large number of cancer cells die rapidly, releasing their contents into the bloodstream. This results in an imbalance of electrolytes, particularly potassium, phosphate, and calcium, as well as an increase in uric acid levels.

**Why the Correct Answer is Right**
TLS is characterized by the release of intracellular contents, including nucleic acids, proteins, and electrolytes, into the bloodstream. This leads to hyperkalemia due to the release of potassium ions from lysed cells, hypocalcemia due to the formation of calcium phosphate complexes, hyperphosphatemia due to the release of phosphate ions, and hyperuricemia due to the breakdown of nucleic acids to uric acid. The kidneys are overwhelmed by the sudden increase in waste products, leading to acute kidney injury.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because TLS is not primarily characterized by hypokalemia. While potassium levels may fluctuate, hyperkalemia is the more common finding.
**Option B:** Incorrect because TLS is not primarily characterized by a decrease in bicarbonate levels. While metabolic acidosis may occur, it is not a defining feature of the syndrome.
**Option C:** Incorrect because TLS is not primarily characterized by an increase in lactate levels. While lactate may be elevated in some cases, it is not a hallmark of the syndrome.

**Clinical Pearl / High-Yield Fact**
In patients with high-risk malignancies, such as acute lymphoblastic leukemia or Burkitt lymphoma, prophylactic measures to prevent TLS, including allopurinol and hydration, should be initiated before chemotherapy.

**Correct Answer: C. Hyperkalemia, hypocalcemia, hyperphosphatemia, and hyperuricemia.**