Cook pasta as directed on package; drain. Return to same pan.
Spray skillet with non stick spray. Add chicken; cook and stir on med-high heat 4 to 5 minutes or until cooked through. Add Velveeta, soup, tomatoes, mushrooms and milk; stir on low heat until cheese is melted. Add chicken mixture to pasta; toss to coat. Spoon into greased 9 x 13 baking dish.
Bake at 350 degrees for 35 to 40 minutes, or until bubbly hot.