Analysis of immunophenotypic changes in acute megakaryoblastic leukemia after treatment

Antigen expression on residual blast cells in acute megakaryoblastic leukemia (AMKL, classified as AML-M7 by FAB criteria) may change after treatment, potentially affecting both immunophenotypic characterization and minimal/measurable residual disease (MRD) monitoring. This study aimed to characterize post-therapy immunophenotypic alterations in AMKL and to determine whether specific patterns of antigenic change exist between samples obtained at initial presentation (IP group) and those obtained at MRD-positive status after therapy (MRD group). This retrospective descriptive study included 110 patients diagnosed with AMKL at Hebei Yanda Lu Daopei Hospital between January 1, 2009 and December 31, 2024 (male:female = 57:53; 103 pediatric and 7 adult cases). Immunophenotypes at initial diagnosis and after treatment were analyzed by flow cytometry. The chi-square test was used to compare antigen expression between the IP and MRD groups. Flow cytometric immunophenotypes differed by at least three antigens (including CD33, CD61, and CD42b) between initial presentation and post-therapy samples. Compared with the IP group, the MRD group showed a significantly higher frequency of loss of megakaryocytic markers, including CD61 (11/109, 10.1% vs. 30/109, 27.5%; p < 0.05) and CD42b (6/106, 5.7% vs. 22/101, 21.8%; p < 0.05). Partial loss of CD13 expression was also more frequent in the MRD group (18/99, 18.2% vs. 2/83, 2.4%; p < 0.05). No significant differences were observed in the expression of progenitor-associated markers (CD34, CD117), myeloid markers (CD33, CD11b), or other antigens (HLA-DR, CD7, CD56, CD42a) between the two groups (p > 0.05). Lineage-specific markers MPO and CD22, the monocytic marker CD14, and lymphoid markers CD10 and CD5 were negative in both groups. In contrast, aberrant expression of cCD3 (2/89, 2.2%) and CD19 (3/85, 3.5%) was observed in a small subset of IP cases. Overall, 100 of 110 patients (90.9%) showed changes in at least one antigen after therapy. By lineage category, alterations were most frequent in megakaryocytic markers (CD61, CD42b, CD41a, CD42a; 64/110, 58.2%), followed by myeloid antigens (HLA-DR, CD33, CD13, CD11b; 54/108, 50.0%), progenitor-associated antigens (CD34, CD117; 53/110, 48.2%), and lymphoid antigens (CD7, CD56; 24/107, 22.4%). In addition, CD110 was consistently expressed in all 26 AMKL cases tested, whereas only 18% (9/50) of non-AMKL AML cases were CD110-positive (p < 0.05). Significant immunophenotypic differences, particularly involving CD61, CD42b, and CD13, exist between IP and MRD samples in AMKL. Antigenic shifts affecting megakaryocytic, myeloid, progenitor-associated, and lymphoid markers are common after chemotherapy. For MRD assessment, the use of more specific megakaryocytic markers such as CD110, together with comprehensive multiparameter flow cytometry panels, may improve detection accuracy.