Bring a large pot of lightly salted water to a boil. Cook macaroni in boiling water for 8 to 10 minutes, or until al dente; drain.
In a medium bowl, combine tuna, condensed soup, and milk. Mix with the macaroni, and pour into 2 quart casserole dish. Sprinkle Cheddar cheese and crushed croutons over top.
Bake in a preheated oven for 20 to 30 minutes, or until bubbling and browned on the top.
