American Society for Clinical Pathology (ASCP) Technologist in Cytogenetics certification (ASCP CG) Practice Test

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What does the designation "M1" indicate about differentiation in this AML subtype?

It indicates full differentiation
It signifies no differentiation at all
It means slight differentiation
It denotes significant chromosomal changes

The correct answer is: It signifies no differentiation at all

The designation "M1" in the context of acute myeloid leukemia (AML) specifically indicates that there is a lack of differentiation in the leukemic cells. In the classification of AML by the French-American-British (FAB) system, M1 refers to acute myeloblastic leukemia without maturation. This means that the leukemic cells are primarily myeloblasts that do not demonstrate significant maturation into more differentiated forms, such as promyelocytes or myelocytes. In contrast, other classifications, such as M2, depict cases where there is some degree of maturation and thus differentiation. The M1 category is associated with a poorer prognosis due to the immature nature of the cells, and therapies are often assessed based on the level of differentiation. The other classifications would denote varying degrees of maturation, which makes it clear that M1 signifies a total absence of differentiation rather than slight differentiation.