An internist is a physician who focuses on the diagnosis and treatment of conditions that affect the adult population—both acute and chronic.
These doctors are often who adults see as their primary physicians because they treat a broad range of illnesses that do not require surgical or specialist interventions. They also work to help a patient maintain optimal health in order to prevent the onset of disease.
In addition to treating the common cold and flu, internists also treat chronic diseases like diabetes and heart disease.

A hematology specialist is an expert in disorders of the blood, the blood forming organs and bone marrow. These doctors diagnose, treat and work to prevent diseases that affect the production of blood and its components, as well as the ability of the blood to perform its many functions, such as coagulation and carrying oxygen to the lungs and tissue.
Hematologists diagnose and treat blood disorders, such as anemia, hemophilia, leukemia, sickle cell anemia, deep vein thrombosis and pulmonary embolism.
Depending on the condition, hematology specialists may treat a patient with a blood transfusion, stem cell transplantation, bone marrow transplant, radiotherapy, anticoagulation therapy or medication.

Think of an oncologist as your main physician for cancer care. After being diagnosed, you’ll meet regularly with an oncologist to explore and manage your treatment options, as well as monitor your condition throughout the process. Medical oncologists are extremely knowledgeable in various types of cancer treatment and can recommend the right method for the type and stage of cancer you’re facing.
They may also refer you to additional specialists throughout your care, but they will always be your home base for questions and support. It’s also worth mentioning that medical oncologists deal mostly with solid tumors while hematologists specialize in cancers that involve blood disorders, such as leukemia.