Paraneoplastic Cast Nephropathy Associated With Pancreatic Acinar Cell Carcinoma: A Kidney Biopsy Teaching Case

Paraneoplastic cast nephropathy, a rare cause of acute kidney injury, is most commonly observed in cases of multiple myeloma and is characterized by the formation of intratubular casts composed of monoclonal light chains. Nonmonoclonal paraneoplastic cast nephropathy has also been reported in patients with pancreatic acinar cell carcinoma or prolactinoma. In this case report, we present a case of polyclonal cast nephropathy in a patient with metastatic acinar cell carcinoma. We aim to emphasize the significance of recognizing this uncommon complication in patients with solid tumors and to discuss the diagnostic challenges and potential pathophysiology of this unique condition.