Pathology of the myeloproliferative diseases

Elevated plasma levels of vascular endothelial growth factor is associated with marked splenomegaly in chronic myeloid leukemia

Recent investigations support the idea that angiogenesis is involved in the pathophysiology of hematologic malignancies, including chronic myeloid leukemia (CML). The aim of the present study was to evaluate plasma levels of VEGF and bFGF in a cohort of 51 chronic-phase CML patients at the time of diagnosis, as well as to investigate the effect of imatinib therapy on VEGF amounts in CML patients. Plasma VEGF levels were significantly higher in patients studied as compared with the 20 healthy subjects (p<0.001), the median plasma VEGF level detected in patients analysed and healthy controls was 433.4 pg mL(-1) (range 65.2-2,452.7 pg mL(-1)) and 81.6 pg mL(-1) (range 44.2-338.7 pg mL(-1)), respectively. On the other hand, no difference in bFGF plasma levels could be found between chronic-phase CML patients and the control group. There were significant associations between plasma VEGF levels and some characteristics of patients evaluated, with trends for higher VEGF values in patients with enlarged spleens (p = 0.02) and those with higher platelet count (p<0.001). Of the patients, 11 received imatinib treatment. The initial VEGF levels markedly decreased after 6 months of imatinib therapy in each patient (p<0.001). These data support the important pathophysiological role of VEGF in CML. Further studies aiming to explore the detailed angiogenic profile of CML may help in developing new therapeutic strategies for this myeloproliferative disorder.

The kinetics of clonal dominance in myeloproliferative disorders

To study clonal evolution in myeloproliferative disorders, we used stochastic models of hematopoiesis for mouse and cat, species for which the in vivo kinetics of hematopoietic stem cells (HSCs) have been experimentally defined. We determined the consequence if 1 HSC became able to survive without the support of a microenvironmental niche while the rest of its behavior did not change. Neoplastic cells persisted and dominated hematopoiesis in 14% of mice and 17% of cats, requiring mean times of 2.5 +/- 0.5 and 7.0 +/- 1.2 years, respectively (n=1000 simulations/species). In both species, when the number of neoplastic HSCs exceeded 0.5% of all HSCs, clonal dominance was inevitable. Our results can explain the absence of clonal myeloproliferative disorders in mice (lifetime, 2 years), are consistent with clinical observations in cats, and provide insight into the progression of chronic myelogenous leukemia (CML) in humans. They also demonstrate that competition for microenvironmental support can lead to the suppression of normal hematopoiesis as neoplasia evolves. Toxic or immunologic suppression of normal HSCs is not required.

Hypereosinophilic syndrome: two case reports of contrasting variants

Two cases of hypereosinophilic syndrome that illustrate different variants are reported. Recognition of the specific variant is important because the treatments differ. Patients with hypereosinophilic syndrome should be monitored for evidence of a myeloproliferative process because treatment with tyrosine kinase inhibitors in these patients is effective and may prevent significant morbidity.

Polycythemia vera

The differential diagnosis of an elevated hematocrit and the criteria for the diagnosis of polycythemia vera present little or no problem; however, there is not a consensus on therapy. Spivak likened this to a conundrum--"an intricate and difficult problem." Nonetheless, it can be argued that on the basis of the following criteria--life expectancy, the absence of toxicity, and long remissions an average of 3.1 years or a median of 2 years--and with acute leukemia no more common than in other regimens except phlebotomy alone (a regimen that cannot be sustained), 32P should be the treatment of choice except in pregnant women. Others, but not all, share this view. This is in contrast to the statement, "Thus chemotherapy treatment of [polycythemia vera] patients is not as easy, innocuous, and well tolerated as it is generally believed". Patients treated with phlebotomy alone were subjected to an unacceptably high incidence of early thrombotic events. Unavailability of pipobroman eliminates this choice.