Conventional, NBI-magnification endoscopic and endocytoscopic appearances and histopathological and immunohistological findings in Case 13 of gastric involvement of adult T-cell leukemia/lymphoma (ATLL). Conventional gastroscopy shows an ulcerative tumor in the upper stomach (A). Magnifying endoscopy using NBI shows irregular microsurface structures including destroyed or dilated gastric pits and nonstructural mucosa devoid of pits and elongated and distorted microvessels (B). Endocytoscopy shows dense aggregation of cellular elements with intensely stained nuclei of various configurations (C). Histopathological examination of targeted biopsies shows diffuse mucosal infiltration of pleomorphic neoplastic cells (hematoxylin and eosin stain, X200, D) with T-cell surface marker (UCHL-1, X200, E).