SUMMARY Therapy-related acute myeloid leukemia (tAML) is one of the two forms of secondary acute myeloid leukemia, with one derived from de novo myelodysplastic syndrome (MDS) and the other from exposure to environmental or therapeutic agents such as radiation and toxins. There has been a marked increase in the number of incidences of therapy-related acute myeloid leukemia. It has become a distinctive disease because of its etiology and genetic tumorigenesis. The majority of tAML resulting from the use of cytotoxic agents can be divided into two groups based on the drugs administered to the patient. The first group includes the use of alkylating agents, and the second group includes agents that bind to the enzyme DNA-topoisomerase Ⅱ. Due to the unfavorable outcome of the disease and the need for prompt intensive treatment, a timely accurate diagnosis of tAML is critical to patient care. Cytogenetic study can detect abnormalities most commonly associated with tAML and thus providing important diagnostic information. However, utilizing cytogenetic analysis alone cannot guarantee prompt and accurate results. In this study, an interesting case with therapy-related myelodysplastic syndrome and acute myeloid leukemia (tMDS/tAML) will be presented. A laboratory diagnostic strategy for tAML laboratory diagnosis will also be proposed.