Paneth Cell Carcinoma of the Stomach

Paneth cell carcinoma is a rare carcinoma composed predominantly or purely of malignant Paneth cells. An 83-year-old woman presented for evaluation of an elevated lesion in the stomach. On endoscopy, a 15 mm, discolored, elevated lesion with a central depression was found on the greater curvature of the gastric lower body. Endoscopic forceps biopsy revealed chronic gastritis with intestinal metaplasia. Magnifying endoscopy revealed an irregularly oval/tubular microsurface pattern and an irregular loop microvascular pattern with a demarcation line, suggestive of early gastric cancer. Therefore, endoscopic submucosal dissection was performed. Histopathological examination revealed a well-differentiated tubular adenocarcinoma limited to the muscularis mucosae and the tumor cells contained coarse eosinophilic granules in the cytoplasm. These tumor cells were diffusely and strongly stained for lysozyme, confirming the tumor diagnosis as Paneth cell carcinoma. Herein, we report a rare case of Paneth cell carcinoma and its endoscopic and histopathologic findings.