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Acute lymphoblastic leukemia with azurophilic granules that contain ultrastructural myeloperoxidase activity
T Tauchi1, K Ohyashiki, J H Ohyashiki
1First Department of Internal Medicine, Tokyo Medical College, Japan.
Insights
This study details a unique case of acute lymphoblastic leukemia (ALL) with myeloperoxidase-positive granules. Findings suggest a rare ALL subtype originating from early stem cells.
Area of Science:
- Hematology
- Oncology
- Cell Biology
Background:
- Acute lymphoblastic leukemia (ALL) is a heterogeneous hematologic malignancy.
- Standard diagnostic criteria for ALL include morphology, immunophenotyping, and cytochemistry.
- Distinguishing ALL from other myeloid leukemias is crucial for appropriate treatment.
Observation:
- A case of ALL presented with cytoplasmic azurophilic granules.
- Leukemic cells expressed lymphoid markers (CD10, CD19, CD20, HLA-DR).
- Light microscopy cytochemistry was negative for myeloperoxidase (MPO), PAS, and esterase.
Findings:
- Ultrastructural analysis revealed MPO-positive cytoplasmic granules.
- This contrasts with typical ALL findings and suggests a myeloid lineage marker.
- The immunophenotype remained consistent with B-cell ALL.
Implications:
- Suggests a potential new subtype of ALL with MPO-positive granules.
- Indicates leukemic transformation may occur at an early pluripotent stem cell stage.
- Highlights the importance of ultrastructural studies in complex leukemia cases.
Abstract:
We present a case of acute lymphoblastic leukemia (ALL) in which the leukemic cells had cytoplasmic azurophilic granules. Surface marker studies revealed that the leukemic cells expressed CD10 (CALLA), CD19, CD20, and HLA-DR antigens. Cytochemical studies by light microscopy revealed that the blasts were negative for myeloperoxidase, PAS staining, and double esterase staining, supporting the diagnosis of ALL. However, an ultrastructural study demonstrated that some of the cytoplasmic granules were myeloperoxidase (MPO) positive. Our findings suggested that leukemic transformation in this case may have taken place at a stage ontogenetically close to the pluripotent stem cell. Furthermore, the present case indicates the existence of a new form of ALL is characterized by MPO-positive granules detectable by ultracytochemistry and lymphoid-associated surface markers.