In previous studies, several cytokines, such as SCF, TNF-α, PDGF, TGF-β, bFGF, PF4, and IL-8 contributed to the expansion of malignant clones from the BM to the spleen as an EMH site, leading to the development of splenomegaly in MF patients. This evidence concerns the gene PF4 and Splenomegaly.