A complete blood count, also called a CBC, can detect some blood cancers based on the amount of certain blood cells in the blood, according to Mayo Clinic. Abnormal blood cells can also be a sign of cancer. A bone marrow test confirms a diagnosis of blood cancer.
Cancers that affect the blood, such as leukemia, lymphoma or multiple myeloma, can cause an increase or decrease in the different types of white blood cells. Cancer can also affect red blood cell counts. A low RBC, along with anemia, can be a symptom of cancer, states American Society of Clinical Oncology. Because there are many types of blood cells, and blood cell abnormalities, there needs to be a comprehensive blood panel analysis before making a cancer diagnosis.