Hematology is a subspecialty of internal medicine or pathology concerned with the development, function, and diseases of the blood, bone marrow, vascular system, spleen, and lymph glands. A hematologist specializes in the diagnosis, treatment, prevention, and investigation of disorders of the hematopoietic, hemostatic, and lymphatic systems as well as disorders of the interaction between blood cells and blood vessel walls. Through investigation and treatment of hematologic malignancies (leukemias and lymphomas), hematology also shares areas of interest and activity with medical oncology. Hematologists use the medical history, physical findings, specialized clinical laboratory tests, and evaluation of tissue or cytological specimens to diagnose and treat disorders of red and white blood cells, platelets, and the blood clotting system, as well as benign and malignant disorders of the bone marrow and lymph glands. They use a broad range of approaches to treat these diseases, including blood products and blood derivatives, nutritional supplements, immunosuppressants, chemotherapy and other anti-tumor agents, pain management, drugs that prevent or promote blood clotting, and stem cell therapies (bone marrow/hematopoietic stem cell transplantation). Not only must hematologists have the clinical skills of general internists, they also need a broad knowledge of cell biology, biochemistry, and laboratory techniques.