Localized amyloidosis of the stomach mimicking a superficial gastric cancer.

A 73-year-old man was referred to our hospital for further examination of a depressed lesion in the stomach found by cancer screening gastroscopy. A barium upper gastrointestinal series showed an area of irregular mucosa measuring 15 mm on the anterior wall of the gastric body. Esophagogastroduodenoscopy revealed a 15 mm depressed lesion on the anterior wall of the lower gastric body. We suspected an undifferentiated adenocarcinoma from the appearance and took some biopsies. However, histology of the specimens revealed amyloidal deposits in the submucosal layer without malignant findings. Congo red staining was positive for amyloidal protein and green birefringence was observed under polarized light microscopy. Congo red staining with prior potassium permanganate incubation confirmed the light chain (AL) amyloid type. There were no amyloid deposits in the colon or duodenum. Computed tomography of the chest, abdomen, and pelvis showed no remarkable findings. Thus, this case was diagnosed as a localized gastric amyloidosis characterized by AL type amyloid deposition in the mucosal or submucosal layer. As the clinical outcome of gastric AL amyloidosis seems favorable, this case is scheduled for periodic examination to recognize potential disease progression and has been stable for 2 years.