<prompt> Paraneoplastic erythrocytosis seen in which malignancy?Renal CaBreast CaThyroid CaAdrenal Ca  <response>: A Renal Ca ERYTHROCYTOSIS Ectopic production of erythropoietin by cancer cells causes most paraneoplastic erythrocytosis. The ectopically produced erythropoietin stimulates the production of red blood cells in the bone marrow and raises the hematocrit, Approximately 3 of patients with renal cell cancer, 10 of patients with hepatoma, and 15 of patients with cerebellar hemangioblastomas have erythrocytosis. In most cases the erythrocytosis is asymptomatic. 