How I investigate acute myeloid leukemia

Acute myeloid leukemia (AML) is a neoplasm of immature myeloid cells and is associated with a wide variety of clinical presentations, morphological features, immunophenotypes, and genetic findings. Recent advances in identification of cytogenetic abnormalities and mutations have provided novel insights into the pathogenesis of AML. Based on the above-mentioned parameters, the World Health Organization (WHO) classified AML into 25 subtypes, including 2 provisional entities, which differ in prognosis and treatment. In addition, certain mutations are associated with germline predisposition and increase the risk of inherited AML, which warrants family screening. Therefore, precise diagnosis and classification of AML are the most important steps in patient management. Both these steps require incorporation of history, clinical presentation, and laboratory results with studies performed by a pathologist. Pathologist-initiated studies include morphologic evaluation on the bone marrow aspirate and/or core biopsy, immunophenotyping by flow cytometry and/or immunohistochemistry, cytogenetic analysis by karyotyping and/or fluorescence in situ hybridization, and molecular testing using gene panels and/or next-generation sequencing. A similar approach is employed during follow-up of patients after beginning treatment. Here, we describe in detail the various aspects of the workup, including purpose, limitations, and practice guidelines for the different studies. The process of choosing appropriate materials for the different studies is also addressed. We also provide an algorithm for the workup and risk stratification of AML based on guidelines recommended by the WHO, College of American Pathologists, National Comprehensive Cancer Network, American Society of Clinical Oncology, European Society of Medical Oncology, and the European LeukemiaNet.