Preheat oven to 425°.
Remove brown gills from the undersides of mushrooms using a spoon; discard gills. Remove and discard stems. Set mushroom caps aside.
Beat cream cheese at medium speed of a mixer until smooth. Add green onions and the next 4 ingredients (green onions through pepper); beat well. Stir in crabmeat, tomatoes, and cheese. Spoon mixture evenly into mushroom caps; sprinkle each cap with 1 tablespoon breadcrumbs, and place on a baking sheet. Bake at 425° for 15 minutes or until tops are lightly browned.