A United Boeing 777-200, registration N783UA performing flight UA-804 from Tokyo Narita (Japan) to Washington Dulles,DC (USA), was in the initial climb out of Tokyo's runway 16R when the crew stopped the climb at 5000 feet reporting smoke in the cabin. The aircraft returned to Tokyo's Narita Airport for a safe landing on runway 16R about 20 minutes after departure. The flight was cancelled. The occurrence aircraft is still on the ground in Tokyo about 37 hours after landing back.