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Immunophenotypic characterisation of acute leukaemia after polycythemia vera
J M Hernández1, A Orfao, M González
1Servico de Hematología, Hospital Clínico Universitario, Salamanca, Spain.
Insights
Acute leukaemia in polycythemia vera patients often involves myeloid blast cells, suggesting a pluripotential stem cell origin. This study analyzed immunophenotype and clinical data in these complex cases.
Area of Science:
- Hematology
- Oncology
- Immunology
Background:
- Polycythemia vera (PV) is a myeloproliferative neoplasm.
- Secondary acute leukaemia can develop after PV treatment.
- Understanding the immunophenotype of these leukaemic cells is crucial.
Purpose of the Study:
- To analyze the immunophenotype of blast cells in patients with acute leukaemia following polycythemia vera.
- To correlate immunophenotypic findings with clinical and haematological characteristics.
Main Methods:
- Immunofluorescence flow cytometry using 15 monoclonal antibodies.
- DNA content analysis of blast cells via Vindelov's technique.
Main Results:
- Patients presented with hepatosplenomegaly, leucocytosis, and thrombocytopenia.
- Blast cells predominantly showed a myeloid phenotype (CD13/33), with some expressing granulomonocytic, erythroid, or megakaryocytic markers.
- Coexpression of lymphoid antigens (CD7, TdT, CD19) was observed in some cases.
- Blast cells exhibited diploid DNA content and a low S-phase fraction.
Conclusions:
- The findings suggest that acute leukaemia developing after PV arises from a pluripotential stem cell committed to myeloid differentiation.
- This highlights the complex cellular origins of secondary leukaemias in myeloproliferative neoplasms.
Aims:
To analyze the immunophenotype of blast cells in patients with acute leukaemia after polycythemia vera, together with the most relevant clinical and haematological disease characteristics.
Methods:
The immunophenotype was analysed in nine patients by immunofluorescence flow cytometry using a panel of 15 monoclonal antibodies. The DNA content of blast cells was determined using Vindelov's technique.
Results:
The most relevant clinical and haematological disease characteristics included: the presence of enlarged spleen and liver by 56% and 67%, respectively; a moderate degree of leucocytosis with thrombocytopenia while haemoglobin was normal in 50% of patients. All patients received alkylating agents or hydroxyurea, or both. Interestingly, the chronic phase in patients receiving this latter drug was shorter. All cases showed a myeloid phenotype, four of them reactive only to early myeloid antigens (CD13/33); in the remaining cases the blast cells displayed granulomonocytic (CD14+, CD15+), erythroid (CD71 ), or megakaryocytic (CD61+, CD41+) markers. Coexpression of lymphoid related antigens (CD7, TdT, or CD19) was also detected. The morphological assessment of blast cells agreed with the immunophenotyping in five out of the nine cases. Blast cells from all six patients analysed displayed a diploid DNA content and the proportion of S-phase cells ranged from 0.4% to 4%.
Conclusions:
These findings suggest a pluripotential stem cell with myeloid commitment as the target cell of acute leukaemia after polycythemia vera.