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Acute megakaryoblastic leukemia in infants with t(1;22)(p13;q13) abnormality
W C Chan1, A Carroll, C S Alvarado
1Department of Pathology/Microbiology, University of Nebraska Medical Center, Omaha 68198-3135.
Insights
This study identifies a unique type of acute megakaryoblastic leukemia in infants with a specific genetic translocation. Early recognition is key for accurate diagnosis and treatment of this rare childhood cancer.
Area of Science:
- Pediatric Hematology Oncology
- Cancer Genetics
- Infant Leukemia Research
Background:
- Acute megakaryoblastic leukemia (AMKL) is a rare subtype of acute myeloid leukemia.
- Infantile AMKL with a t(1;22)(p13;q13) translocation presents unique diagnostic challenges.
Purpose of the Study:
- To characterize the clinical, pathological, and immunophenotypic features of infantile AMKL with t(1;22)(p13;q13).
- To establish diagnostic criteria for this specific leukemia subtype in infants.
Main Methods:
- Analysis of clinical data, bone marrow morphology, and histology from six infants with AMKL and t(1;22).
- Immunophenotyping of peripheral blood and paraffin-embedded tissues using monoclonal antibodies.
- Cytogenetic analysis to identify the t(1;22)(p13;q13) translocation.
Main Results:
- All patients presented with hepatosplenomegaly and anemia; four had thrombocytopenia.
- Bone marrow showed prominent fibrosis in most cases, complicating histological interpretation.
- Immunophenotyping confirmed megakaryoblastic lineage and differentiated AMKL from other small round cell tumors, notably neuroblastoma.
- The t(1;22)(p13;q13) translocation was a consistent finding.
Conclusions:
- Infantile AMKL with t(1;22)(p13;q13) has distinct clinical and pathological features.
- Accurate diagnosis relies on integrating clinical presentation, morphology, immunophenotype, and cytogenetics.
- Awareness of these features aids in confident recognition and differentiation from other pediatric malignancies.
Abstract:
Six infants with acute megakaryoblastic leukemia and a translocation (1;22)(p13;q13) were studied. There were five female infants and one male infant, and the age at initial examination varied from 0.8 to 6.5 months (median, 2.3 months). All the patients had hepatosplenomegaly and anemia (6 to 8.3 g/dL), and four patients had thrombocytopenia (9,000 to 63,000/mm3). The bone marrow showed prominent fibrosis in five cases and reticulin fibrosis in one patient at presentation. Crush artifact often made the histologic sections difficult to interpret, but typical megakaryoblasts could be identified in the smears. Biopsy specimens of the liver and lymph node were suggestive of a nonhematopoietic malignant condition because of the cohesiveness of the tumor cells, stromal fibrosis, and the prominent sinusoidal and vascular pattern of infiltration. Immunophenotyping of peripheral blood mononuclear cells was helpful in identifying the blasts as belonging to the megakaryoblastic lineage. Using a panel of mononclonal antibodies, it was also possible to confirm the nature of the infiltration in paraffin sections and to differentiate it from other childhood small round cell tumors, especially neuroblastoma in paraffin sections (typical staining pattern: CD45-, CD43+, vW Factor, Ulex europeus I+, CD20-, CD45RO-, synaptophysin-, chromogranin-, cytokeratin-, desmin-). This special type of infantile acute leukemia can be recognized with confidence if one is aware of its clinical features, peculiar pathologic characteristics, the morphologic features and immunophenotype of the megakaryoblasts, and the unique cytogenetic abnormality.