Case presentation
A 73-years-old man had been on peritoneal dialysis for 9 years for chronic renal failure due to immunoglobulin A nephropathy and had switched to hemodialysis 3 years before the operations.
He had been taking lanthanum carbonate for seven years. Several months after lanthanum carbonate initiation, regular endoscopy revealed white granular lesions on the gastric mucosa at the gastric body and fundus (Fig.1-A). A biopsy of these lesions revealed chronic active inflammation with regenerative epithelium, intestinal metaplasia, and lanthanum deposition. Regular annual endoscopy revealed that these lesions had grown, changed morphologically, and spread gradually (Fig.1-B), but they showed no malignancy. Two months before the operation, regular endoscopy revealed a gradually growing, reddish, and elevated mucosa surrounded by white granular mucosa in the gastric antrum (Fig.2-A). Narrow band imaging (NBI) showed no signs of malignancy, such as an irregular microvascular pattern (Fig.2-B), but histological examination revealed well-differentiated adenocarcinoma. The clinical stage was T1bN0M0 stage I based on the TNM classification specified by the International Union Against Cancer (UICC). The boundary between the adenocarcinoma and mucosal changes with lanthanum deposition was unclear by endoscopy with NBI, and neoplastic lesions seemed to be spread around the gastric body. Therefore, we planned to perform a surgical operation to achieve curative resection and laparoscopic distal gastrectomy with lymph node dissection. Histopathological examination revealed a well-differentiated tubular adenocarcinoma, which was limited to the antrum surrounded by lanthanum nodules (Fig.3-A). The tumor was limited to the mucosa at the gastric antrum, and the pathological stage was T1aN0M0 stage I. Lanthanum deposition was observed in the lamina propria of the carcinoma and gastric mucosa (Fig.3-B). Histological alterations, such as glandular atrophy and hyperplasia, were also observed. The resected lymph nodes also included lanthanum deposits eaten by macrophages (Fig.3-C). In the interstitium of cancerous and non-cancerous lesions, lanthanum was mostly eaten by macrophages that expressed CD68 (Fig.4-A, B).