Paraneoplastic Cast Nephropathy Associated With Pancreatic Mixed Acinar-Neuroendocrine Carcinoma: A Case Report

Acute kidney injury is common in patients with cancer and may result from sepsis, obstruction, radiotherapy, chemotherapeutic agents, and nonsteroidal anti-inflammatory drugs. Rare reports of acute kidney injury due to cast nephropathy in patients with pancreatic acinar cell carcinoma have been described, but a pathogenetic link between cast nephropathy and carcinoma was not established. We report a patient with pancreatic mixed acinar-neuroendocrine carcinoma who developed severe acute kidney injury. Kidney biopsy showed cast nephropathy characterized by fractured periodic acid-Schiff-negative casts, associated with mononuclear and giant cell reaction. The patient did not have multiple myeloma and casts did not show immunoglobulin light chain restriction on immunofluorescence. Analysis using liquid chromatography-tandem mass spectrometry and immunohistochemistry identified 2 acinar cell-specific proteins, regenerating islet-derived 1α and carboxypeptidase A1, in both tubular casts and tumor cells. Thus, this case demonstrates that solid tumor-specific proteins can be nephropathic by obstructing renal tubules, resulting in acute kidney injury, a previously proposed but not characterized pathophysiologic mechanism for paraneoplastic nephropathy associated with carcinoma.