What happened, in summary

An 88-year-old Japanese man was referred for worsening swelling and heavy protein loss in the urine. He had gained 7.8 kg from fluid retention, with edema affecting both legs, the abdomen, and the scrotum. A kidney biopsy was performed, and an upper endoscopy was added because nephrotic syndrome can sometimes be linked to an underlying malignancy. Endoscopy found a type 1 stomach tumor, and biopsy confirmed adenocarcinoma.

Although he was 88, his overall health and cognitive function were good enough for curative surgery. On hospital day 34, he underwent distal gastrectomy, and the tumor was completely resected. Pathology showed an 80 by 55 mm papillary adenocarcinoma with pT1aN0M0 disease and a surrounding foveolar-type adenoma. Most malignant areas had an intestinal phenotype and expressed MUC2 and CDX2. THSD7A staining was positive in the intestinal-type adenocarcinoma but negative in the foveolar-type adenoma.

The kidney biopsy showed THSD7A-positive membranous nephropathy. Because the same marker was present in the gastric cancer and the kidney disease improved after tumor removal, the team considered the nephropathy associated with the cancer. He was managed conservatively without immunosuppressive drugs. Within 3 months of surgery, the nephrotic syndrome improved. The early postoperative course therefore showed complete gastric tumor removal together with improvement of the cancer-associated kidney condition.