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Diagnosis:
Acute Promyelocyctic Leukemia (APL), FAB-M3
ISCN: 46,XX(15;17)(q22;q12)
Cytogenetics: The 15;17 translocation
occurs in 10-15% of adult AML cases. It occurs in both the hypergranular
and microgranular variant of APL. The 15;17 translocation is present is
seen in about 95% of cases of APL. Rare variants account for less than
5% of cases of APL and include t(11;17)(q23;q12), t(5;17)(q35;q12), t(11;17)(q13;q12),
and t(17;17)(q11;q12). The 15;17 translocation occurs as the sole chromosomal
abnormality in approximately 60% of APLs, and along with other chromosomal
abnormalities in approximately 40% of APLs. The most common secondary
chromosomal abnormality is an extra chromosome 8 which is seen in about
10% of cases of APL.
Molecular:The gene at 15q22 is called
PML and codes for zinc finger protein that appears to act as a tumor suppressor.
The gene at 17q12 is called RARA and codes for the retinoic acid receptor
alpha that is a nuclear, ligand-inducible transcription factor. The 15;17
translocation creates a PML-RARA fusion protein. RARA also rarely (greater
than 5% of APLs) partners with other genes instead of PML; these other
genes include PLZF (11q23), NPM (5q35), NuMA (11q13), and Stat5b (17q11).
Web Links: Atlas
of Genetics and Cytogenetics in Oncology and Haematology
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