Aberrant CD25 and Increased CD123 Expression Are Common in Acute Myeloid Leukemia with KMT2A Partial Tandem Duplication and Are Associated with FLT3 Internal Tandem Duplication.

BACKGROUND

KMT2A partial tandem duplication (PTD) occurs in approximately 5-10% of acute myeloid leukemia (AML) cases and is associated with poor prognosis. While its cytogenetic and molecular features are well described, the immunophenotypic characteristics of AML with KMT2A-PTD remain incompletely defined.

METHODS

We identified 47 cases of AML with KMT2A-PTD by optical genome mapping. All cases underwent flow cytometric immunophenotypic analysis and next-generation sequencing using an 81-gene panel.

RESULTS

The cohort included 32 men and 15 women with a median age of 67 years (range, 19-87). Thirty-eight cases were de novo AML, and nine were secondary to myelodysplastic syndrome and/or myeloproliferative neoplasm. Most cases (93%) demonstrated a normal or non-complex karyotype. The most frequent mutations involved FLT3-ITD (47%), DNMT3A (43%), and RUNX1 (23%). Thirty-one cases (66%) were granulocytic, while 16 (34%) showed granulocytic and/or monocytic differentiation. Blasts uniformly expressed HLA-DR and frequently expressed CD117 (91%) and CD34 (79%). Increased expression of CD123 (74%) and CD117 (43%) and decreased expression of HLA-DR (74%) and CD38 (69%) were common. Aberrant CD25 expression was observed in 51% of cases. Increased CD123 and aberrant CD25 expression were significantly associated with FLT3-ITD mutations (both p < 0.0001) but not with other recurrent mutations. There was no correlation between FLT3-ITD mutation and expression levels of CD117, CD38 or HLA-DR (all p > 0.05).

CONCLUSIONS

AML with KMT2A-PTD shows distinctive immunophenotypic features with increased CD123 and aberrant CD25 expression, both associated with FLT3-ITD. These markers may have diagnostic and therapeutic relevance in this AML subtype.