Carcinoma of the ampulla of Vater with membranous nephropathy: a case report.

Nephrotic syndrome can occur secondary to malignancy, and its resolution is sometimes observed following tumor resection. We herein report the case of a 67-year-old Asian man who presented with membranous nephropathy associated with carcinoma of the ampulla of Vater. The patient initially presented with edema, hypoalbuminemia, and significant proteinuria with positive PLA2R antibody. Following surgical removal of the tumor, his urinary protein levels normalized, his serum albumin returned to normal, and the nephrotic syndrome achieved complete remission. This case underscores the importance of screening for secondary causes, such as malignancies, in patients with nephrotic syndrome. For those with malignancy-associated nephrotic syndrome, prompt and targeted treatment of the underlying tumor is critical to avoid missing the window for surgical intervention. This report aims to provide insights into the diagnosis and management of tumor-associated nephrotic syndrome, contributing to a better understanding of this rare clinical entity.