Pretreatment tumor lysis syndrome associated with bulky retroperitoneal tumors. Recognition is the mainstay of therapy.

Acute pretreatment tumor lysis syndrome is a rare complication of cancer. Early recognition and aggressive management are mandatory for prevention of the adverse sequelae of the syndrome. Here we present 2 cases of pretreatment tumor lysis syndrome, concluding that this clinical entity should be in the differential diagnosis of acute renal failure associated with malignancy, as early recognition is in fact the mainstay of treatment.