t(8;21)(q22;q22)
The t(8;21) rearrangement is almost exclusively observed in acute nonlymphocytic leukemia (ANLL) and specifically in acute myloid leukemia (AML:FAB M2).  The t(8;21) is also associated with a large number of cells showing auer rods.  Additional chromosome changes are observed in over 75 percent of t(8;21) cases which also include the loss of a sex chromosome, a deleted 9q, trisomy 8, and monosomy 7.  The presence of the t(8;21) alone has been reported to indicate a relatively good patient  prognosis.