Various hematologic abnormalities have been associated with RCC. Anemia has been reported in 28 % - 88 % of patients diagnosed with RCC, and may be the presenting symptom in 10 %. The anemia is typically nor-mochromic and normocytic, and consistent with that observed in chronic disease. Leukocytosis and throm-bocytosis are also observed occasionally in patients with RCC. Some correlation of platelet levels with IL-6 levels has been shown. IL-6 is known to stimulate thrombopoiesis in murine and primate animal models. Leukocytosis could be related to tumor necrosis or could be cytokine-mediated. The presence of receptors for granulocyte-macrophage colony stimulating factor (GM-CSF) has been reported in vitro on some transformed renal cell lines. Pancytopenia has occurred occasionally in patients with RCC. It is almost always associated with disease involvement of the bone marrow (DaSilva et al. 1990; Shiramizu et al. 1994).
The occurrence of erythrocytosis in renal cell carcinoma was first reported in 1929 (Bliss 1929). However, erythropoietin production by the tumor was well documented in the early 1990s (DaSilva et al. 1990; Shiramizu et al. 1994). Erythrosis generally was considered to be a paraneoplastic phenomenon because elevated erythropoietin levels were observed in patients diagnosed with RCC. Paraneoplastic erythrocytosis is differentiated from polycythemia vera by the absence of leukocytosis, thrombocytosis, and splenomegaly, and from secondary polycythemia by the absence oflow arterial oxygen saturation (Bliss 1929). Cell lines from human renal cell carcinoma have been shown to produce erythropoietin. It has been suggested that eryth-ropoietin secreting renal tumors may be responsive to therapy IL-2 and alpha-IFN. However, this study included only five patients, which makes it difficult to draw a definitive conclusion (Janik et al. 1993).
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