Case Presentation: A 38-year-old woman with suspected metastatic right breast cancer presented to the acute care hospital for a second opinion. The patient first noticed a breast lump one year ago and had been receiving homeopathic medical care without improvement. She was evaluated in a foreign country one week prior to admission and was advised to transition to comfort care. Her vitals were notable for tachycardia (HR 120s) and tachypneic (RR 30s). Her right breast was diffusely enlarged and firm without any erythema, induration, or discharge. Labs were notable for a creatinine 1.29 mg/dL, calcium 14.3 mg/dL, and lactate 3.4 mmol/L. A computed tomogram (CT) of the head, chest, and abdomen/pelvis showed diffuse metastatic disease to the calvarium, thoracic spine, and liver. She was admitted for treatment of suspected hypercalcemia of malignancy and further cancer workup. A core biopsy confirmed estrogen receptor positive (ER+), progesterone receptor negative (PR-), and human epidermal growth factor receptor-2 positive (HER2+) Grade 3 invasive ductal cell carcinoma of the right breast. Oncology was consulted and hormone therapy was initially considered.Two days into her hospitalization, however, a rapid response event was called for acute encephalopathy. Labs revealed a creatinine 1.74 mg/dL, potassium 6.8 mmol/L, phosphorus 7.0 mg/dL, calcium 9.3 mg/dL, uric acid 13.8 mg/dL, lactate dehydrogenase >2500 U/L––consistent with spontaneous tumor lysis syndrome. She was quickly started on aggressive medical management with high-rate intravenous fluids and bicarbonate, sodium zirconium, intravenous furosemide, and needed a one-time dose of rasburicase 6 mg. Unfortunately, the patient continued to exhibit significant electrolyte derangements despite above measures and transitioned to comfort care three days later.
Discussion: Tumor lysis syndrome (TLS) is an oncologic emergency that arises from the rapid breakdown of tumor cells, leading to significant metabolic disturbances. While TLS is most commonly observed in patients undergoing treatment for hematologic malignancies; it can also occur spontaneously but rarely in solid tumors. So far to best of our knowledge, there are less than 40 reported cases of spontaneous TLS in solid organ malignancies, with less than ten of these cases in metastatic breast cancer.Prognosis of spontaneous TLS typically depends on the underlying malignancy and tumor burden. However, studies suggest mortality is significantly higher in patients with TLS from solid tumors. It stands to reason that prognosis may be even more grim for those who suffer spontaneous TLS from solid tumors given its rarity and the potential for delayed workup and diagnosis. In this case, the patient’s acute kidney injury was attributed to a prerenal etiology. It is unclear whether her renal function was actually a warning sign for a more serious sequalae to come.
Conclusions: This case emphasizes the importance of maintaining a high index of suspicion for TLS in all patients with malignancies, whether hematologic or solid, treated or untreated. Providers must pay close attention to individual risk factors and consider spontaneous TLS on their differential for electrolyte abnormalities or renal failure in those considered potentially high risk. Unfortunately, this patient’s clinical status continued to deteriorate despite appropriate and aggressive management, highlighting the need for earlier diagnosis and treatment of spontaneous TLS.