For the crab cakes: Whisk together the mayonnaise, Worcestershire, seafood seasoning, scallions, egg, lemon zest and 1/2 teaspoon salt in a large bowl. Add the bread and toss to coat.
Add the crab and combine the mixture well with your hands. Form 18 small crab cakes, about 2 inches wide and 1/2-inch thick, making sure to pack the cakes tightly with your hands.
Heat the butter in a large nonstick skillet over medium heat until the foam subsides. Working in batches, add the crab cakes and cook, turning once, until golden brown on both sides and heated through, about 3 minutes per side.
For the mango salsa: Combine the cilantro, sugar, cucumber, lemon juice, mango and jalapeno in a medium bowl and season with salt.
For the creamy Dijon: Combine the mayonnaise and Dijon in a small bowl and mix well.
Serve the hot crab cakes topped with a dollop of the creamy Dijon and a little of the salsa.