Tartrate resistant acid phosphatase stain is useful in diagnosing which leukemia?

The tartrate resistant acid phosphatase (TRAP) stain is particularly significant in diagnosing hairy cell leukemia. This type of leukemia is characterized by the presence of hairy cells, which are mature B-cells that exhibit a distinct morphology and functional properties. In hairy cell leukemia, these cells demonstrate strong positivity for the TRAP stain, which helps differentiate this condition from other types of leukemias.

The relevance of the TRAP stain lies in its ability to reveal the enzymatic activity associated with hairy cells, providing a critical diagnostic tool in identifying this specific leukemia. This is why the correct answer is associated with hairy cell leukemia, as it is the only leukemia among the choices provided that shows a characteristic response to the TRAP stain.