Answer
There are too few cases of acute undifferentiated leukemia (AUL) to determine whether there is an associated consistent genetic abnormality, although expression of some genes associated with an unfavorable prognosis in AML (eg, BAALC, ERG, MN1) may be seen.
As described with regard to mixed phenotype acute leukemia (MPAL) with t(9;22)(q34;q11.2) (or BCR-ABL1 rearrangement) and MPAL with t(v;11q23) (or KMT2A (MLL) rearrangement), these leukemias are defined by the consistent presence of their respective genetic abnormalities. Of note, it appears that patients with MPAL with t(9;22) may respond favorably to treatment with tyrosine kinase inhibitors (TKI). [11] The most common partner gene in the KMT2A (MLL) rearrangement is AF4 on chromosome 4, band q21. [12, 13] Translocations t(9;11) and t(11;19) are also encountered.
MPALs (B/myeloid and T/myeloid) commonly have clonal cytogenetic abnormalities. In the B/myeloid type, complex karyotypes are often seen, and abnormalities encountered in more than one single case include the following: del(6p), 12p11.2 abnormalities, del(5q), structural abnormalities of 7, and numeric abnormalities, including near tetraploidy. [12, 13] Moreover, alterations have been identified in the following genes that are also associated with either acute myeloid leukemia (AML) or acute lymphoblastic leukemia (ALL): ASXL1, TET1, TET2, IDH1, IDH2, DNMT3A, NOTCH1, ETV6, and IKZF1. Despite these genetic characteristics, there are insufficient data to designate any of these changes as recurrent.
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Pathology of Acute Leukemias of Ambiguous Lineage. Blasts of acute undifferentiated leukemia.
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Pathology of Acute Leukemias of Ambiguous Lineage. Blasts of mixed phenotype acute leukemia with t(4;11q23).
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Pathology of Acute Leukemias of Ambiguous Lineage. Blasts of acute myeloid leukemia, type M0.
