Prepare macaroni according to package directions, omitting salt.
Meanwhile, combine undrained tomatoes and cheese in 1-1/2-quart microwavable dish; cover. Microwave on MEDIUM (50%) 10 to 12 minutes or until cheese melts, stirring after 6 minutes. Add milk; stir mixture until well blended.
Drain macaroni; place in large bowl. Add cheese mixture; toss to coat.