Faggot formation in mature neutrophils and metamyelocytes in acute myeloid leukemia without maturation.

The authors report a rare case of acute myeloid leukemia (AML) M1 with faggot formation in mature neutrophils and metamyelocytes. Although Auer rods in mature neutrophils are occasionally experienced, they are usually found in AML M2, M3, or M4 cases, but not in M1 cases. In addition, faggot formation in mature neutrophils, as seen in this case, is considered to be particularly unusual because most previously reported cases tended to show simple Auer rods except for AML M3 cases. This case also showed trisomy 4 in its karyotype, although its relationship with faggot formation remains unclear.