I never use “discontinue approach”. (Too easily misunderstood - was that “continue”, “just continue” or “discontinue”? I’ve heard it misunderstood on both sides of the mic.
If aircraft is in level flight I’d say “maintain altitude [x] thousand feet, continue present heading, this will be a missed approach.”
If aircraft is in descent but has not yet reached the missed approach altitude I’d say “stop descent at [x] thousand feet, continue present heading, this will be a missed approach.”
(Then coordinate with radar.)