Upper GI endoscopy is the best test to diagnose gastric cancer because it lets you see the lesion and take multiple biopsies from the edges of the ulcer.

• A barium meal (upper GI series) should not be done when GI bleeding is suspected (anemia + occult blood here), and it cannot give tissue.
• CT is used for staging (local invasion, nodes, metastases), not for diagnosis; ultrasound has no role in diagnosing the primary.