Supernumerary isochromosome 4p in ANLL-M4 myelomonocytic type is associated with favorable prognosis

A case of an acute non-lymphocytic leukemia of M4 type with a supernumerary isochromosome (4p) in 100% of the initial bone marrow metaphase cells is reported. The origin of the extra chromosome is verified by the fluorescence in situ hybridization technique using a whole chromosome 4 painting probe. A possible favorable prognosis of the ANLL-M4 case showing a supernumerary isochromosome (4p) is cautiously emphasized.