Minimal Coexpression of CD34+/CD56+ in Acute Promyelocytic Leukemia Is Associated With Relapse
Thomas M Maenhout1, Elisabeth Moreau2, Inge Van Haute2
1From the Departments of Laboratory Medicine and Department of Laboratory Medicine, Ghent University Hospital, Ghent, Belgium. Thomas.Maenhout@ugent.be.
Objectives:
Surface CD56 expression on leukemic cells in acute promyelocytic leukemia (APML) is considered an indicator of poorer outcome even in patients receiving conventional treatment.
Methods:
In the present case, at initial diagnosis, the hallmark phenotype of APML was found (strong CD33 and cytoplasmic MPO expression, absence of HLA-DR expression).
Results:
Both CD34 and CD56 antigen expression was considered negative. The patient relapsed 3 years after reaching complete remission, and the hallmark surface antigen combination for APML was again found. In contrast, the leukemic cells now clearly coexpressed CD34 and CD56. Retrospective analysis revealed the presence of small CD34+ and CD56+ populations at initial diagnosis (<20%).
Conclusions:
This case report suggests that the presence of a clone with minimal coexpression of CD34/CD56 in APML at initial diagnosis should not be neglected since it may be associated with earlier relapse.
Insights
Minimal CD34/CD56 expression in acute promyelocytic leukemia (APML) at diagnosis may indicate earlier relapse. This finding highlights the importance of detecting even small leukemic cell clones for better prognosis in APML patients.
Area of Science:
- Hematology
- Oncology
- Immunophenotyping
Background:
- Acute promyelocytic leukemia (APML) is a distinct subtype of acute myeloid leukemia.
- Surface CD56 expression on APML cells typically indicates a poorer prognosis.
Observation:
- A case of APML initially negative for CD34 and CD56 expression.
- The patient relapsed after 3 years with CD34 and CD56 coexpressing leukemic cells.
- Retrospective analysis identified a small CD34+/CD56+ clone at initial diagnosis.
Findings:
- The presence of a minimal CD34+/CD56+ clone in APML at diagnosis was observed.
- This clone was associated with a relapse occurring earlier than expected.
- CD34 and CD56 expression can evolve during the course of APML.
Implications:
- Minimal CD34/CD56 coexpression in APML may be a predictor of early relapse.
- Rethinking the prognostic significance of CD56 in APML.
- The importance of sensitive immunophenotyping for detecting minimal residual disease and predicting outcomes in APML.
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