Cook macaroni according to package directions.
Drain and combine with mushroom soup, onion, broccoli, cheese, pimento and mayonnaise, mixing well. Place combined ingredients in a greased 13-by-9-inch baking dish.
Combine butter and crumbs, mixing well; distribute evenly over mixture in dish and sprinkle lightly with paprika. Bake at 350 degrees for 30 minutes.