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Guide And Atlas For The Detection Of Minimal Residual Disease In AML

Cytogenetics and AML

Cytogenetic monitoring of the clinical course of AML is often associated with a specific chromosomal change, ie, t(8;21) in M2. Establishment of the change at diagnosis allows recognition of the leukemic cells in the marrow when relapse or residual disease is to be evaluated. It also provides a prognostic determinant. The three karyotypes shown depict stages of AML during the course of the treated disease.[4]

M2 with a recurrent genetic abnormality

M2, acute myeloblastic leukemia with maturation. The sum of the myeloblasts is greater than 30% but less than 90%. Pseudo- Pelger-Hut cells and hypogranular neutrophils are present. Blasts often contain many granules, and the nuclei may have a prominent nucleolus. Thin Auer rods are easily visible. This type of marrow cytology is often seen in the M2 type of AML with t(8;21)(q22;q22).[4]

t(8;21) at diagnosis. The karyotype at diagnosis with a t(8;21)(q22;q22) (arrows) as the only cytogenetic change. This translocation is usually seen in AML (M2) often associated with Auer rods, marrow eosinophilia, and a favorable prognosis.[4,16]

Normal chromosomes during complete remission. All chromosomes appear normal. No karyotypes with t(8;21) were seen.[4]

Chromosomes at relapse, t(8;21) and trisomy 8(+8). The reappearance of the t(8;21) (long arrows) is shown and, most importantly, the presence of trisomy 8(+8) (short arrow) as a new karyotypic change. Generally, the appearance of additional chromosomal changes is associated with biologic progression of the leukemia.[4]

M4 with chromosome and gene involvement

M4, acute myelomonocytic leukemia (AMML). Immature cells from the marrow of a patient with M4 showing both granulocytic and monocytic features.[4]

Translocation (6;9). Shown in this partial karyotype is the translocation (6;9)(p22;q34) seen in AML M4 (or M2) and often associated with marrow basophilia: breakpoints are indicated by arrows.[4]

Gene involvement. In the schematic presentation of the translocation, the genes involved are DEK-CAN, as shown.[4]

M3 with t(15;17)

M3, acute promyelocytic leukemia (APL). Hypergranular blasts predominate. Cells contain bundles of delicate, needlelike Auer rods. The t(15;17), which is characteristic of this type of leukemia, is also seen in the hypogranular form of this leukemia (M3v). It is generally associated with a favorable prognosis.[4,16]

Translocation (15;17)(q22;q12). The breakpoints on this partial karyotype are indicated by arrows.[4]

PML-RAR-alpha gene involvement. This schematic presentation of the translocation (15;17)(q22;q12), characteristic of APL (M3), involves the genes PML-RAR-alpha.[4]

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