A mass lesion presenting difficulty in differential diagnosis between a tumor in the lateral segment of the liver and a gastric submucosal tumor (SMT) was found in a 59-year-old man with chronic hepatitis B. For differential diagnosis between the 2 lesions, endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) was performed. EUS showed a tumor exhibiting a mosaic pattern with a halo derived from the lateral segment of the hepatic left lobe in contact with the stomach. FNA using the cell block technique revealed findings consistent with HCC. No examination-associated complications developed. In patients with HCC that is in contact with the stomach and shows extrahepatically protruding growth, which is difficult to differentiate from gastric SMT, EUS-FNA is a method worthy of trying.