The
paraneoplastic syndrome (PNS) is an association of symptoms and signs not directly related to the site or local manifestations of a malignant
tumor or its
metastases. Hematologic abnormalities as PNS include
erythrocytosis,
anemia, neutrophilia,
neutropenia,
eosinophilia,
thrombocytosis,
thrombocytopenia,
venous thromboembolism and
disseminated intravascular coagulation (
DIC). These abnormalities are, by and large, due to the production of biologically active
growth factors,
hormones or as yet unidentified "humors" by the
tumor. As our understanding of
growth factors controlling hematopoiesis has increased in recent years, the
biologic basis of hematologic PNS are better understood. For instance,
tumor-associated neutrophilia is now known to be caused by the production of
G-CSF by the
tumor. The mechanism by which
tumor causes
thromboembolism have also been extensively investigated.
Cancer cells induce platelet aggregation both in vitro and in vivo. Platelet aggregating material has been isolated and partially characterized from
tumor cells. The involvement of
platelet glycoprotein II b/IIIa in the
tumor-platelet interaction has also been shown. Malignant cells contain a unique procoagulant,
cancer procoagulant A, that directly activates
factor X. Together with
tissue factor, this procoagulant appears to have been contribute to a high incidence of
thromboembolism in
cancer patients. Better understanding of hematologic PNS is important for clinical care of the patients with
cancer.