Diagnosis often begins with blood tests that can show abnormal levels of blood cells. However, a definitive diagnosis usually requires a bone marrow biopsy. In this procedure, a sample of bone marrow is extracted and examined under a microscope. Histological examination can reveal the presence of abnormal cells, such as blasts in leukemia or Reed-Sternberg cells in Hodgkin lymphoma. Immunohistochemistry and flow cytometry are also commonly used to identify specific cell markers.
