Tumours of the haematopoietic and lymphoid tissues are tumours that affect the blood, bone marrow, lymph and lymphatic system. As these tissues are all closely linked through both the circulatory and immune systems, disease affecting one will often affect the others, making aplasia, myeloproliferation and lymphoproliferation (and hence leukaemias and lymphomas) closely related and often overlapping problems. Although rare in solid tumours, chromosomal translocations are a common cause of these diseases. This often leads to a different approach to the diagnosis and treatment of haematological malignancies. Haematological malignancies are malignant neoplasms ("cancers") and are usually treated by specialists in haematology and/or oncology. In some centres, 'haematology/oncology' is a single subspecialty of internal medicine, while in others it is considered a separate department (there are also surgical and radiation oncologists). Not all haematological disorders are malignant ('cancerous'); these other blood disorders may also be treated by a haematologist.
Blood cancer, also known as hematologic cancer, is a type of cancer that affects the blood, bone marrow, and lymphatic system. There are three main types of blood cancer:
Leukemia: This type of cancer affects the blood and bone marrow. It occurs when the body creates too many abnormal white blood cells, which impairs the bone marrow's ability to produce red blood cells and platelets. ** There are four main types of leukemia:
Acute myeloid leukemia (AML)
Acute lymphoblastic leukemia (ALL)
Chronic myeloid leukemia (CML)
Chronic lymphocytic leukemia (CLL)
Lymphoma: This type of cancer affects the lymphatic system, which is part of the immune system. Lymphoma occurs when abnormal lymphocytes, a type of white blood cell, multiply and collect in the lymph nodes and other tissues. ** There are two main types of lymphoma:
Hodgkin lymphoma
Non-Hodgkin lymphoma
Myeloma: This type of cancer affects plasma cells, which are a type of white blood cell that helps produce antibodies. Myeloma occurs when abnormal plasma cells multiply in the bone marrow and form tumors. ** There are two main types of myeloma:
Multiple myeloma
Waldenstrom macroglobulinemia
Haematological malignancies can arise from either of the two main blood cell lineages: myeloid and lymphoid. The myeloid line normally produces granulocytes, erythrocytes, platelets, macrophages and mast cells; the lymphoid line produces B, T, NK and plasma cells. Lymphomas, lymphocytic leukaemias and myelomas are of lymphoid origin, whereas acute and chronic myeloid leukaemias, myelodysplastic syndromes and myeloproliferative disorders are of myeloid origin.
A subset of these are more severe and are known as haematological malignancies or blood cancers. They may also be called liquid tumours.
When a haematological malignancy is suspected, a complete blood count and a blood film are essential, as malignant cells can have a characteristic appearance on light microscopy. If there is lymphadenopathy, a biopsy of a lymph node is usually taken surgically. A bone marrow biopsy is usually part of the work-up for these diseases. All samples are examined microscopically to determine the type of malignancy. A number of these diseases can now be classified by cytogenetics (AML, CML) or immunophenotyping (lymphoma, myeloma, CLL) of the malignant cells.
Historically, haematological malignancies were most commonly classified according to whether the malignancy was primarily in the blood (leukaemia) or in the lymph nodes (lymphoma).
Treatment may sometimes consist of watchful waiting (e.g. CLL) or symptomatic treatment (e.g. blood transfusions in MDS). The more aggressive forms of the disease require treatment with chemotherapy, radiotherapy, immunotherapy and, in some cases, bone marrow transplantation. The use of rituximab has been established for the treatment of B-cell haematological malignancies, including follicular lymphoma (FL) and diffuse large B-cell lymphoma (DLBCL).
In addition to curative treatment, people may benefit from self-care to manage symptoms. For example, aerobic exercise, such as walking, can reduce fatigue and feelings of depression in people with haematological malignancies.
If treatment is successful ("complete" or "partial remission"), a person is usually followed up at regular intervals to check for recurrence and to monitor for "secondary malignancy" (a rare side effect of some chemotherapy and radiotherapy - the appearance of another form of cancer). Follow-up examinations, which should be carried out at predetermined regular intervals, combine a general medical history with a complete blood count and a serum measurement of lactate dehydrogenase or thymidine kinase. Haematological malignancies and their treatment are associated with complications affecting many organs, most commonly the lungs.
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