Acute promyelocytic leukemia: four distinct patterns by flow cytometry immunophenotyping

Area of Science:

• Hematology
• Oncology
• Immunophenotyping

Background:

• Acute promyelocytic leukemia (APL) is a distinct subtype of acute myeloid leukemia.
• Accurate diagnosis of APL is crucial for timely and appropriate treatment.
• Flow cytometry (FC) is a valuable tool in the immunophenotypic characterization of leukemia.

Purpose of the Study:

• To analyze the immunophenotypic patterns of acute promyelocytic leukemia (APL) using flow cytometry.
• To identify distinct FC patterns associated with classical and variant forms of APL.
• To improve the identification of APL patients requiring urgent genetic confirmation.

Main Methods:

• Analysis of 97 APL patients with adequate flow cytometry data and confirmed t(15;17)/PML-RARA.
• Characterization of leukemic cell immunophenotype including CD markers and side scatter (SSC) properties.
• Classification of cases into four distinct FC patterns based on immunophenotype and SSC.

Main Results:

• Four FC patterns were identified in APL patients.
• Pattern 1 represented classical (hypergranular) APL with high SSC and specific marker expression.
• Patterns 2, 3, and 4 represented less common variants, including hypogranular APL and mixed populations, with distinct immunophenotypic features.

Conclusions:

• Flow cytometry can distinguish classical and variant immunophenotypes of APL.
• Identification of less common FC patterns aids in recognizing APL.
• These findings support the use of FC in conjunction with genetic testing for rapid APL diagnosis.