What characteristic feature is associated with the leukemia known as acute lymphoblastic leukemia (ALL)?

Acute lymphoblastic leukemia (ALL) is characterized by the proliferation of immature lymphoid cells, commonly referred to as "blasts". These blasts are large, with a high nuclear-to-cytoplasmic ratio and can be identified in blood smears and bone marrow examinations. The presence of these lymphoblasts is a key diagnostic criterion for ALL and is a significant feature that differentiates it from other types of leukemia.

While neutrophil count may fluctuate, and platelet counts can be low in ALL, it is the presence of the lymphoblasts that is distinctive and ultimately crucial for both diagnosis and understanding the disease process. Stain positivity for myeloperoxidase is typically associated with myeloid leukemias rather than lymphoid leukemias such as ALL. Thus, being able to identify blasts confirms the diagnosis of acute lymphoblastic leukemia.