[Diagnostic spectrum of Philadelphia-chromosome negative leukemic disorders]

The spectrum of Philadelphia-chromosome negative leukemoid disorders displays a large heterogeneity of clinical and morphological findings at presentation. According to the FAB guidelines as well as the WHO classification, independent subtypes with different morphological features can be distinguished. In particular, based on the degree of dysgranulopoiesis, the extent of monocytosis, basophilia and the amount of immature and mature granulocytes in the peripheral blood and the percentage of erythroblasts, most of these cases can be correctly classified as either atypical chronic myeloid leukemia (aCML) or chronic myelomonocytic leukemia (CMML). An increase in immature and dysplastic granulocytes in the blood films at presentation accompanied by granulocytic dysplasia, is the most important diagnostic parameter of aCML. On the other hand, CMML is characterized by absolute monocytosis and, as explicitly outlined by the WHO classification, may show myelodysplastic and myeloproliferative features. However, in the absence of characteristic cytogenetic or molecular abnormalities for both diseases, a minority of patients still remain who are difficult to assign to a distinctive entity, since they either show overlapping features or do not fulfill the whole set of diagnostic criteria. Furthermore, controversy and discussion arise about aCML with monocytosis and its association to CMML. Finally, leukemoid reactions and the very rarely encountered chronic neutrophilic leukemia (CNL) should be considered in patients with chronic leukocytosis. In conclusion, careful morphological analysis of bone marrow histology as well as peripheral blood films and bone marrow smears, enables the identification of patients with different prognosis and therapeutic response.