Oncology is a branch of medicine that deals with the prevention, diagnosis, and treatment of cancer. A medical practitioner who practices oncology is called an oncologist. Some of the wide ranges of acute and chronic problems that can be treated by oncologists are, the diagnosis, treatment, and prevention of blood diseases (hematology) and cancer (oncology) and research into them. Hematology-oncology includes such diseases as iron deficiency anemia, hemophilia, sickle cell disease, thalassemias, leukemias, and lymphomas, as well as cancers of other organs. Patients can consult online with an oncologist doctor for non-emergency problems, oncologist advice, for the second opinion of an oncologist, and for follow-ups cases.