Prep: 10 minutes; Cook: 2 minutes
1. Combine first 4 ingredients in a medium bowl. Divide tuna mixture into 4 equal portions, shaping each into a 3/4-inch-thick patty.
2. Heat a large nonstick skillet over medium heat. Coat pan and patties with cooking spray. Add patties; cook 1 to 2 minutes on each side or until lightly browned.
3. While patties cook, combine cucumber and mayonnaise in a small bowl. Serve with tuna cakes.