A hematologist-oncologist is a physician who has trained in both hematology (the study of blood and blood-forming tissues) and oncology (the study and treatment of cancer). Many doctors pursue both specialties together because blood disorders and cancer are closely linked—cancers like leukemia, lymphoma, and multiple myeloma originate in blood cells or bone marrow, and cancer treatments often affect blood counts and clotting.
Training path: In the United States, this typically means completing medical school, an internal medicine residency, and then a combined hematology-oncology fellowship (usually 2-3 years), followed by board certification in both internal medicine subspecialties. In some countries, hematology and oncology remain separate specialties, and a "hematologist-oncologist" credential may not exist in the same combined form.
What they treat:
- Blood cancers: leukemia, lymphoma, multiple myeloma
- Solid tumor cancers: breast, lung, colon, prostate, and others
- Non-cancerous blood disorders: anemia, clotting disorders (like hemophilia or thrombosis), sickle cell disease, and platelet disorders
What they do day-to-day:
- Diagnose conditions using blood tests, bone marrow biopsies, and imaging
- Develop and oversee treatment plans, including chemotherapy, immunotherapy, targeted therapy, and stem cell/bone marrow transplants
- Manage side effects of cancer treatment, such as low blood counts or bleeding risks
- Coordinate care with surgeons, radiation oncologists, and other specialists
- Monitor patients long-term for recurrence or complications
When you might see one: A primary care doctor typically refers patients to a hematologist-oncologist after abnormal blood test results, a suspicious biopsy, or a new cancer diagnosis. Some hematologist-oncologists focus more on cancer care, others more on blood disorders, and some split their practice between both, depending on their training and the needs of their community or hospital system.
Because the field spans both malignant and benign conditions, these specialists play a central role in cancer centers and comprehensive care teams.