Preheat oven to 325°. In a large saucepan, cook broccoli in boiling water for 1 minute; drain. Set aside.
In a large bowl, combine soup, mayonnaise and lemon juice; add broccoli and chicken. Gently stir to combine; transfer to a greased 11×7-in. baking dish. Sprinkle with cheese. Combine bread crumbs and butter; sprinkle over the top.
Bake, uncovered, until bubbly and golden brown, about 30 minutes. Let stand for 10 minutes before serving. If desired, garnish with pimientos.