Oncologic emergencies are life-threatening complications arising from cancer or its treatment that require immediate recognition and intervention. Tumor lysis syndrome (TLS) occurs when rapid cancer cell destruction (typically after chemotherapy for hematologic malignancies) releases intracellular contents: potassium (hyperkalemia causing cardiac arrhythmias), phosphate (hyperphosphatemia causing calcium-phosphate crystal deposition and hypocalcemia), uric acid (hyperuricemia causing acute kidney injury from crystal nephropathy), and nucleic acids. The metabolic triad is hyperkalemia + hyperphosphatemia + hyperuricemia with resultant hypocalcemia. Superior vena cava (SVC) syndrome results from compression or thrombosis of the SVC, most commonly by lung cancer (especially small cell) or lymphoma. Impaired venous drainage from the upper body causes facial/neck/upper extremity edema, JVD, dyspnea, and cough. It can progress to cerebral edema and airway compromise. Spinal cord compression occurs when tumors (commonly breast, lung, prostate metastases) compress the spinal cord, causing back pain, motor weakness, sensory loss, and bowel/bladder dysfunction. This is a neurologic emergency — permanent paralysis results if not treated within 24-48 hours. Hypercalcemia of malignancy occurs in 10-30% of advanced cancers through PTHrP secretion (squamous cell carcinomas), osteolytic bone destruction (multiple...