In acute myelocytic leukemia, what distinguishes type II blasts from type I blasts?

In acute myelocytic leukemia (AML), type II blasts can indeed be distinguished from type I blasts primarily by their cytoplasmic characteristics. Type II blasts typically contain a moderate number of cytoplasmic granules, while type I blasts generally have fewer granules. This difference in granule presence points to how maturation occurs within the myeloid lineage and reflects the cell's functional state.

The presence of Auer rods, which are needle-like cytoplasmic inclusions, tends to be more associated with type I blasts, rather than type II. Characteristics such as large nucleoli and a high nucleus-to-cytoplasm ratio are common in both types of blasts and do not provide a distinguishing feature between them in the context of AML. Therefore, the distinguishing factor is indeed the presence of few cytoplasmic granules in type I blasts compared to type II blasts. Understanding these details is crucial for classifying and diagnosing different subtypes of acute myeloid leukemia accurately.