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Acute myelomonocytic leukemia associated with abnormalities of chromosome 16: a light and electron microscopic study
W T Dalton1, M J Ahearn, A Cork
1Division of Laboratory Medicine, University of Texas System Cancer Center, Houston 77030.
Abstract:
We investigated the light and ultrastructural morphology of 37 patients with acute nonlymphocytic leukemia (ANLL) and inv(16)(p13q22) or del (16)(q22) with specific emphasis on the changes in the eosinophils (EOS). All but one of the 37 patients were classified as French-American-British M4 with eosinophilia (FAB M4-E) on the basis of the monocytoid nature of the leukemic cells and the presence of large EOS with interspersed basophilic-staining granules. A median of 92% of the blasts were peroxidase positive, and Auer rods were found in 71% of cases. Only 27% of the cases had sufficient alpha-naphthyl butyrate positivity to confirm the diagnosis of FAB M4, but electron microscopy demonstrated a sufficient monocytic component to support this classification in all cases examined. Electron microscopy also demonstrated nuclear blebs both in the blasts and notably, in the EOS of all cases examined (16 of 16). Nuclear blebs in EOS were found in only 1 of 13 cases of ANLL that showed eosinophilia but lacked abnormalities of chromosome 16. This case was also classified as FAB M4-E. The finding of nuclear blebs in EOS in FAB M4-E suggests that the EOS may be derived from the malignant clone in this leukemia. These blebs are also of diagnostic in value classifying a leukemia as FAB M4-E.
Insights
Nuclear blebs in eosinophils (EOS) of acute nonlymphocytic leukemia (ANLL) patients with chromosome 16 abnormalities suggest EOS may originate from the malignant clone. This finding aids in classifying ANLL as French-American-British M4 with eosinophilia (FAB M4-E).
Area of Science:
- Hematology
- Oncology
- Cell Biology
Background:
- Acute nonlymphocytic leukemia (ANLL) with chromosome 16 abnormalities, specifically inv(16)(p13q22) or del(16)(q22), often presents as French-American-British M4 with eosinophilia (FAB M4-E).
- The precise origin of eosinophilia in FAB M4-E remains an area of investigation.
Purpose of the Study:
- To investigate the light and ultrastructural morphology of eosinophils (EOS) in ANLL patients with chromosome 16 abnormalities.
- To determine if eosinophils in FAB M4-E leukemia originate from the malignant clone.
Main Methods:
- Light and electron microscopy were used to examine bone marrow morphology in 37 ANLL patients with chromosome 16 abnormalities.
- Immunohistochemical staining for peroxidase and alpha-naphthyl butyrate was performed.
- Comparison was made with ANLL cases showing eosinophilia but lacking chromosome 16 abnormalities.
Main Results:
- All but one patient with chromosome 16 abnormalities were classified as FAB M4-E.
- Electron microscopy revealed nuclear blebs in blasts and, notably, in eosinophils of all examined cases (16 of 16) with chromosome 16 abnormalities.
- Nuclear blebs in eosinophils were rare in ANLL with eosinophilia but without chromosome 16 abnormalities (1 of 13 cases).
Conclusions:
- The presence of nuclear blebs in eosinophils of FAB M4-E patients suggests that eosinophils may be derived from the malignant clone.
- Nuclear blebs in eosinophils are a valuable diagnostic marker for classifying leukemia as FAB M4-E.