Hematologic oncology is a medical specialty that merges the sciences of haematology and oncology. Hematology is the study of blood, while oncology is the study of cancer. Hematologic oncologists are doctors who specialise in the diagnosis, treatment, and prevention of blood malignancies and diseases. Hematologic oncologists use a variety of diagnostic methods, including imaging and laboratory tests, to treat patients with malignant hematologic illnesses. They also give sophisticated medical therapy. Hematologic malignancies are distinct from other cancers in that they grow in the body's blood cells and do not always become tumours. While some hematologic oncologists specialise on treating solid malignancies, others do not. The phrase "haematologist oncologist" refers to two groups of physicians. Hematologists are doctors who specialise in the diagnosis and treatment of blood illnesses. Oncologists are doctors who specialise in cancer diagnosis and treatment. A haematologist oncologist is an expert in both fields.