Answer to Question 1
ANS: B
Hairy cells are positive for acid phosphatase when tartrate is added to the incubation mixture. They uniquely contain an abundance of acid phosphatase isoenzyme 5; all other isoenzymes of acid phosphatase, found in almost all other blood cells, are inhibited in the presence of tartrate. At least two or more cells should contain >40 red granules to call the stain positive.
Answer to Question 2
ANS: D
The fact that mature neutrophils stain positive has no diagnostic significance in a patient with acute leukemia. Only examination of the blast cells is useful.