With the development of cytogenetics and molecular biology, researchers have gradually strengthened their understanding of acute leukemia (AL). Morphology, immunology, cytogenetics, and molecular biology (MICM) are widely used in the world, which is not only of great significance to study the pathogenesis and biological characteristics of leukemia, but also of practical value to guide clinical treatment and prognosis judgment. According to its basic immunophenotype, AL is usually classified as acute myeloid leukemia (AML), acute B lymphoid leukemia (B-ALL), and acute T lymphoid leukemia (T-ALL). However, there is a type of ambiguous lineage,which we call mixed phenotype acute leukemia (MPAL). MPAL is an extremely rare type, accounting for about 2–5% of all AL.(1, 2) It is characterized by the detection of at least two of three expression markers in myeloid lineage, B lineage and T lineage.
The current diagnosis of MPAL is mostly based on the relevant standards revised by World Health Organization (WHO) in 2016. Based on the updated WHO classification of hematological malignancies, MPAL can be divided into several subtypes including MPAL with t(9;22)(q34.1;q11.2); BCR-ABL1, MPAL with t(v;11q23.3); KMT2A rearranged, MPAL, B/myeloid, not otherwise specified (NOS) and MPAL, T/myeloid, NOS. (3)MPAL is one of highly heterogeneous malignancies, and the clonal origin of MPAL cells is still unclear. It may be derived from early hematopoietic stem cells and differentiate into myeloid and lymphoid leukemia cells during the development of AL. There is at present no unified treatment for this special type of leukemia. It is controversial on whether MPAL should be treated with a single chemotherapy or combined with chemotherapy for both lymphoid and myeloid leukemia, and whether bone marrow or peripheral blood stem cell transplantation is required. Thankfully, cell and molecular genetic abnormalities such as chromosomal translocations and gene mutations can be detected in most MPAL patients, which are of great significance for guiding the treatment and prognosis of MPAL patients. (2, 4)
Here we reported an extremely rare case of MPAL, T/AML(M5) with PML-RARα rearrangement and t(15;17). We discussed his diagnosis, treatment process and outcome in detail, and combined with literature review, in order to provide experience for the early diagnosis and treatment of similar patients.