The branch of medicine that studies the causes, treatment and prevention of blood-related diseases is known as hematology. Hematologic malignancy is a type of cancer that originates in blood-forming tissues such as the bone marrow or in the cells of the immune system. It is caused by cells dividing at an abnormal rate. The three main types of hematologic malignancies include, leukemia, lymphoma and multiple myeloma. A cancer that begins in the lymphatic system is called lymphoma. The lymphatic system is an important part of the immune system and it includes lymph nodes, spleen, thymus gland and bone marrow. Lymphoma cancer can affect any part of the lymphatic system. Multiple myeloma is a cancer that originates in the bone marrow. It affects the plasma cells. In multiple myeloma, the plasma cells affected with cancer, start building-up in the bone marrow along with the healthy blood cells. Leukemia is a cancer that starts developing in the bone marrow, or blood-forming tissues, or the lymphatic system. The diagnosis includes various blood tests, such as complete blood count (CBC) test and electrophoresis blood test. This book includes some of the vital pieces of works being conducted across the world on various topics related to diagnosis, treatment and control of hematologic malignancies. Students, researchers, hematologists, and all associated with this subject will benefit alike from it.