Fill 3-quart saucepan 2/3 full of water; heat to boiling. Add Pasta. Gently boil, uncovered 12 minutes, stirring occasionally; drain. Rinse with cold water to cool; drain well.
In small bowl, combine Seasoning mix from packet and mayonnaise. In large bowl, gently toss seasoning mixture, chicken, corn, tomatoes and cheese until mixed; stir in cooked pasta. Top with cilantro, if desired.