In which type of leukemia are the blasts typically positive for periodic acid-Schiff (PAS) staining?

The type of leukemia where the blasts are typically positive for periodic acid-Schiff (PAS) staining is acute lymphoblastic leukemia (ALL). PAS staining is particularly useful in identifying certain leukemias because it highlights glycogen and mucoproteins present in the cytoplasm of specific cell types. In ALL, the blasts frequently show a strong positive reaction to PAS, indicating the presence of these substances. This positive staining not only aids in the diagnosis but also helps in differentiating ALL from other types of leukemia, making it an important tool in the hematopathology laboratory.

In contrast, the other types of leukemia listed do not consistently show this positive PAS staining in their blasts. Chronic myeloid leukemia (CML) is characterized primarily by the presence of myeloid cells, while acute myelogenous leukemia (AMML) does not typically exhibit the same degree of PAS positivity as ALL. Chronic lymphocytic leukemia (CLL) involves small, mature lymphoid cells that also do not present with the PAS positive blasts seen in ALL. Therefore, recognizing the significance of PAS staining is crucial for accurate diagnosis and classification within hematologic malignancies.