They found that a type of fat or type of cholesterol called cholesteryl-alpha-D-glucopyranoside plays a key role in helping it to grow.

BBC: Clues to beating stomach cancer

Dzhokhar communicated with his interrogators in writing, precluding the type of back-and-forth exchanges often crucial to establishing key facts, said the officials, who spoke on condition of anonymity because they were not authorized to discuss the investigation publicly.

NPR: Boston Bomb Suspect Charged; Religious Motive Seen