Secondary erythrocytosis involves increased erythropoietin (EPO) signalling in the bone marrow. Several types of neoplasm are known to produce excess EPO, including renal cell carcinoma, uterine fibroids, hemangioblastoma, and hepatocellular carcinoma. EPO production can also be increased following renal transplant Ref: Verhovsek M., McFarlane A. (2012). Chapter 173. Abnormalities in Red Blood Cells. In G.V. Lawry, S.C. McKean, J. Matloff, J.J. Ross, D.D. Dressler, D.J. Brotman, J.S. Ginsberg (Eds), Principles and Practice of Hospital Medicine.