The Ultrastructure of Hybrid Acute Leukemia: A Study of 15 Cases

Activation of monocyte-derived cells in the bone marrow of myelodysplastic syndrome

OBJECT

To study the relationship between monocyte/histiocyte activation and myelodysplastic syndrome (MDS).

METHODS

Analyzing ultrastructure and myeloperoxidase reaction of nucleated cells in bone marrow from 59 cases of MDS by transmission electron microscopy. Four groups of MDS were subdivided on the basis of their content of activated inflammatory cells - morbid hematopoiesis with minimal inflammatory cell activation (MH-MICA); MDS with monocytic system activation (MSA); MDS with lymphocyte activation (LCA); and MDS with granulocyte activation (GCA).

RESULTS

About 20, 22, 7, and 10 cases were classified as MH-MICA (34%), MSA (37%), LCA (12%), and GCA sub-types (17%), respectively. About 3, 5, 0, and 3 cases from MH-MICA, MSA, LCA, and GCA, respectively, underwent leukemic transformation within 2 years.

CONCLUSION

The findings suggest that activation of inflammatory cells in bone marrow is an important feature of MDS, and that monocytes/histocytes are perhaps the most prominent cellular participants in the pathogenesis of MDS.

Invasion of erythroblasts by Pasmodium vivax: A new mechanism contributing to malarial anemia

Severe malarial anemia causes considerable mortality and morbidity in endemic areas. Possible mechanisms underlying the anemia include lysis of parasitized and nonparasitized red cells as well as parasite product-mediated effects on erythropoiesis. The latter include suppression of erythropoiesis, dyserythropoiesis, and ineffective erythropoiesis. Present transmission electron microscope data in two cases of Pasmodium vivax malaria show a hitherto undescribed mechanism contributing to malarial anemia, namely, infection of erythroblasts by parasites and their subsequent degradation. No parasites were detected in the peripheral blood but parasites were found in the bone marrow. These findings emphasise the value of bone marrow examination in the diagnosis and eradication of malaria.

Significance of transmission electron microscopy in subtyping of monocytic leukemia

The objective of this paper is to produce an ultrastructural classification of acute monocytic leukemia (AML-M5) in relation to clinical behaviors. The ultrastructural characteristics of blasts of the monocytic series were analyzed in 72 M5 patients by transmission electron microscopy (TEM), in terms of their content of typical monoblasts, atypical monoblasts, atypical promonocytes, and typical promonocytes in bone-marrow aspirates. Four kinds of monocytic blasts were identified by cell size and shape, nuclear profile, nucleocytoplasmic ratio, heterochromatin content, nucleolus, granules, vesicles, and Golgi apparatus. Their characteristics of remission rate, cytochemistry, immunophenotype, and cytogenetics were also investigated. The data obtained permitted M5 patients to be divided into monoblast and promonocyte types. Monoblast-type patients expressed weaker monocytic enzymograms and specific antigen staining for CD14 and CD64, compared with promonocyte-type patients. Monoblast patients had higher CR than promonocyte patients. Therefore, TEM subclassification of patients differs from and improves upon the light microscopical criteria for distinguishing monoblasts and promonocytes and has clinical significance.

Acute leukemia of ambiguous lineage, biphenotype, without CD34, TdT or TCR-rearrangement

Biphenotypic acute leukemia (BAL) is a rare entity that comprises 0.5-3% of all acute leukemias and probably arises from multipotent progenitor cells. The optimal approach for BAL therapy is unknown. Thus, it is important to elucidate the origin of the neoplastic cells for determination of the appropriate therapy. We report the case of a 41-year-old man with BAL having myeloid and T-lymphoid lineage phenotypes. Strangely, neither CD34 nor TdT expression nor rearrangement of TCR-alpha/beta, delta/gamma genes were shown. This pattern is rarely encountered and suggests that the blast cells were possibly considered immature with aspects of differentiation indicating myeloid lineage, rather than T-lymphoid lineage.