In addition, occasionally, cytological features of AML with abnormal eosinophils may be present without karyotypic evidence of a chromosome 16 abnormality, but with CBFB-MYH11 nevertheless demonstrated by molecular studies such as a reverse-transcriptase–polymerase-chain-reaction (RT-PCR) or fluorescent in situ hybridization (FISH), as shown in Figure 3. The gene discussed is CBFB; the disease is acute myeloid leukemia.