In a large skillet, saute spinach in oil for 2-3 minutes or until wilted. Remove and set aside. In the same skillet, cook beef over medium heat until no longer pink; drain. Stir in pizza sauce; cook for 5 minutes or until heated through.
Place crusts in an ungreased 15x10x1-in. baking pan; spread with meat sauce to within 1/2 in. of edges. Layer with spinach, tomatoes, cheese and pine nuts. Bake at 450° for 8-10 minutes or until heated through.