In a small bowl, combine tuna, mayonnaise, pineapple, pineapple juice, tomato, green onion, Worcestershire sauce, salt, and pepper. Mix well.
Spray a skillet with cooking spray and bring to medium heat. Add pineapple rings (will probably need to be done in a couple batches), then top each ring with a heaping 1/3 cup of tuna salad.
Top each tuna melt with a slice of cheese and let cook for about five minutes, covered with a lid, to allow cheese to melt. Before serving, you can also transfer the pan to an oven set to broil for a couple of minutes until cheese is dotted with brown.
Use a spatula to transfer each tuna melt on to a fresh lettuce leaf for serving. Enjoy!