Leukemia is able to affect humans.
Bone marrow . In humans , red blood cells are produced by cores of bone marrow in the heads of long bones in a process known as hematopoiesis . On average , bone marrow constitutes 4 % of the total body mass of humans ; in an adult having 65 kilograms of mass ( 143 lbs ) , bone marrow typically accounts for approximately 2.6 kg . Leukemia . Leukemias and lymphomas both belong to a broader group of tumors that affect the blood , bone marrow , and lymphoid system , known as tumors of the hematopoietic and lymphoid tissues . In children under 15 , the five-year survival rate is greater than 60 to 85 % , depending on the type of leukemia .