Related Experiment Videos
[M3 variant leukemia: clinical and diagnostic features]
Abstract:
Acute promyelocytic leukemia represents 5-10% of acute myeloid leukemia cases (AML) recorded in the literature, occurring more frequently in young adults. It has a special clinical and biological behaviour when compared to the other forms of AML, being characterized by a particular morphology of blast cells (M3 in FAB classification), translocation of chromosomes 15;17, and disseminated intravascular coagulation at diagnosis or after the onset of chemotherapy. Within this AML subgroup there are 2 morphological subsets called the hypergranular promyelocytic leukemia and the hypogranular or variant form. We have studied clinical and laboratory aspects of 19 cases of AML M3 out of 217 AML cases, and observed a high incidence of failure to recognize the M3 variant form, although its diagnosis has been mainly based on cytomorphology. Only 4 out of 8 cases of the variant form received in our laboratory were correctly diagnosed, being the other 4 cases wrongly identified as the myelomonocytic subset of AML (M4). Immunophenotyping with monoclonal antibodies using CD2 and CD7 as T cell markers, CD10 and CD19 as B cell markers and CD33, CD13, CD14, CD15 and anti MPO as myeloid markers is a complementary diagnostic tool that permits solving difficult cases. It is important to classify AML correctly because of the special therapeutic and prognostic features of AML M3, which differently from other AML forms, has been successfully treated with cellular differentiating agents.
Insights
Acute promyelocytic leukemia (APL) is a distinct subtype of acute myeloid leukemia (AML). Misdiagnosis of the hypogranular APL variant is common, highlighting the need for advanced diagnostic tools.
Area of Science:
- Hematology
- Oncology
- Cell Biology
Background:
- Acute promyelocytic leukemia (APL) accounts for 5-10% of acute myeloid leukemia (AML) cases.
- APL is characterized by a specific blast cell morphology (M3), a 15;17 chromosomal translocation, and disseminated intravascular coagulation.
- Two morphological subsets exist: hypergranular and hypogranular (variant) APL.
Purpose of the Study:
- To investigate the clinical and laboratory aspects of APL.
- To assess the diagnostic accuracy of cytomorphology for the hypogranular APL variant.
- To evaluate the utility of immunophenotyping in diagnosing challenging APL cases.
Main Methods:
- Retrospective analysis of 19 APL cases out of 217 AML cases.
- Diagnosis primarily based on cytomorphology.
- Immunophenotyping using a panel of monoclonal antibodies (CD2, CD7, CD10, CD19, CD33, CD13, CD14, CD15, anti-MPO).
Main Results:
- A high rate of misdiagnosis was observed for the hypogranular APL variant.
- 4 out of 8 variant cases were misclassified as acute myelomonocytic leukemia (AML M4).
- Immunophenotyping proved effective in resolving diagnostic ambiguities.
Conclusions:
- Accurate classification of APL is crucial due to its unique therapeutic and prognostic implications.
- Immunophenotyping serves as a valuable complementary tool for diagnosing difficult APL cases, especially the variant form.
- APL has shown successful treatment outcomes with cellular differentiating agents.