Cutaneous myelofibrosis, also known as cutaneous extramedullary hematopoiesis (CEH), is a chronic myeloproliferative disease characterized by clonal proliferation of defective multipotent cells in the bone marrow. Excessive production and premature death of atypical megakaryocytes in the bone marrow produce large amounts of platelet-derived growth factor, which is a powerful stimulator of fibroblast proliferation and collagen fiber production. Extramedullary hematopoiesis is a hallmark of myeloid fibrosis. A large number of blasts and committed stem cells escape from the bone marrow, enter the blood circulation, and form similarly atypical clonal tumors in other organs, especially the spleen, liver, and lymph nodes.