A Rare Syndrome in a Rare Carcinoma: A Case of Spontaneous Tumor Lysis Syndrome in Small-Cell Liver Carcinoma.

Spontaneous tumor lysis syndrome (STLS) is a rare, oncologic emergency, consisting of life-threatening acute renal failure, hyperuricemia, hyperkalemia, and hyperphosphatemia, prior to the initiation of cytotoxic therapy. Here, we describe a case of STLS in a patient with newly diagnosed small-cell liver carcinoma (SCLC). A 64-year-old female with no significant past medical history presented with a one-month history of jaundice, pruritus, pale stools, dark urine, and right upper quadrant pain. CT of the abdomen revealed a heterogeneous-enhancing intrahepatic mass. CT-guided biopsy of the mass revealed SCLC. At follow-up, labs were significant for potassium 6.4 mmol/L, phosphorus 9.4 mg/dL, uric acid 21.4 mg/dL, calcium 9.0 mg/dL, and creatinine 6.9 mg/dL. She was admitted and treated with aggressive fluid rehydration and rasburicase, with eventual improvement in renal function and normalization of electrolytes and uric acid levels. On the rare occasion that STLS occurs in solid tumors, lung, colorectal, and melanoma are most common, with liver metastases occurring in 65% of cases. Our patient's SCLC was a primary liver malignancy with a large tumor burden, both of which may have predisposed her to develop STLS. Rasburicase is the first line in the treatment of acute tumor lysis syndrome as it quickly decreases uric acid. Identifying SCLC as a risk factor for STLS is key. Due to the high morbidity and mortality associated with this rare phenomenon, a prompt diagnosis is required.