Hematologists specialize in diseases of the blood, bone marrow, spleen, and lymph glands. They treat conditions such as anemia, clotting disorders, sickle cell disease, hemophilia, leukemia and lymphoma. They administer chemotherapy and perform bone marrow transplantation. Medical oncologists specialize in the diagnosis and treatment of all types of cancer and other benign tumors. They administer chemotherapy as well as work with primary care physicians and other medical specialists.