In a large skillet, melt butter; sauté onion and celery until tender. Stir in tuna, soup, mayonnaise, milk, mushrooms, parsley, and pimiento. In a 2-quart buttered casserole, combine hot cooked noodles and the tuna mixture. Top with buttered bread crumbs. Bake at 350° for 25 to 30 minutes, until lightly browned, hot, and bubbly.
