Hematological malignancies are a diverse group of cancers originating in blood-forming tissues, the bone marrow, and immune system cells. These diseases affect the body’s “liquid” tissues, contrasting with solid tumors. They disrupt the normal production and function of blood cells.
Major Categories of Blood Cancers
Blood cancers are broadly categorized into leukemia, lymphoma, and myeloma. Leukemia primarily involves the bone marrow and blood, characterized by the uncontrolled proliferation of abnormal white blood cells. This overproduction interferes with the bone marrow’s ability to produce healthy blood cells, including red blood cells, platelets, and other white blood cells. Leukemias are classified as acute, developing rapidly with immature cells, or chronic, progressing slowly with more mature cells.
Lymphoma originates in the lymphatic system, a network of immune defense vessels and organs. This cancer involves lymphocytes accumulating in lymph nodes, spleen, thymus, and bone marrow. Lymphomas are divided into two types: Hodgkin lymphoma, characterized by Reed-Sternberg cells, and non-Hodgkin lymphoma, a diverse group lacking these cells.
Multiple myeloma is a cancer of plasma cells, a type of white blood cell in the bone marrow. Plasma cells produce antibodies that fight infection. In multiple myeloma, abnormal plasma cells multiply uncontrollably, producing dysfunctional antibodies and crowding out healthy blood cells. This accumulation can lead to bone damage, kidney problems, and a weakened immune system.
Common Symptoms and Signs
Individuals with hematological malignancies may experience a range of non-specific symptoms. Persistent fatigue is a common complaint, often resulting from anemia due to reduced red blood cell production. Easy bruising or bleeding, such as frequent nosebleeds or prolonged bleeding from minor cuts, can indicate low platelet counts. Swollen, painless lymph nodes in the neck, armpits, or groin may suggest lymphoma, as these are areas where lymphocytes congregate.
Systemic symptoms, often referred to as “B symptoms,” include unexplained fevers, drenching night sweats, and significant, unintentional weight loss. Frequent infections are another common sign, occurring when the body’s white blood cells are suppressed or dysfunctional. Bone pain, especially in the back or ribs, can be a symptom of conditions like multiple myeloma, where cancerous cells can weaken bones.
The Diagnostic Process
Diagnosing hematological malignancies begins with a medical history and physical examination, followed by specialized tests. A complete blood count (CBC) is often performed, providing information about the number of red blood cells, white blood cells, and platelets. An abnormal CBC, such as very high or very low white blood cell counts, anemia, or low platelet counts, can raise suspicion. A peripheral blood smear allows doctors to observe the shape and maturity of blood cells and identify abnormal cells.
If blood tests suggest a malignancy, a bone marrow aspiration and biopsy are performed. During this procedure, a small amount of liquid bone marrow (aspiration) and a tiny piece of solid bone marrow (biopsy) are collected, typically from the hip bone. These samples are then analyzed to identify cancer cells, assess the percentage of abnormal cells, and determine the specific type of malignancy. For suspected lymphomas, a lymph node biopsy may be performed, involving surgical removal for microscopic examination.
Imaging tests, such as computed tomography (CT) scans and positron emission tomography (PET) scans, are used to determine the extent of the disease, often referred to as staging. A CT scan provides detailed images of internal organs and lymph nodes, helping to identify enlarged nodes or masses. A PET scan uses a radioactive tracer that accumulates in metabolically active cancer cells, providing a comprehensive view of disease distribution throughout the body.
Approaches to Treatment
Treatment strategies for hematological malignancies are varied and depend on the specific type of cancer, its stage, and the patient’s overall health. Chemotherapy is a common approach, using powerful drugs to kill rapidly dividing cancer cells throughout the body. These drugs can be administered intravenously or orally to destroy cancer cells and reduce tumor burden. Radiation therapy uses high-energy rays to target and destroy cancer cells in specific areas, often employed to shrink tumors, alleviate pain, or prepare for stem cell transplantation.
Targeted therapy is a precise approach, focusing on specific molecular abnormalities within cancer cells that promote their growth and survival. Unlike traditional chemotherapy, which affects both healthy and cancerous cells, targeted drugs are designed to interfere with particular proteins or pathways unique to cancer cells, potentially leading to fewer side effects. Immunotherapy harnesses the body’s own immune system to fight cancer. This involves stimulating the immune system to attack cancer cells or providing engineered immune components, such as antibodies, to target specific cancer markers.
Stem cell transplantation involves replacing diseased or damaged bone marrow with healthy blood-forming stem cells. This procedure is often used after high-dose chemotherapy or radiation, which can destroy the patient’s own bone marrow. The new stem cells can come from the patient’s own body (autologous transplant) or from a donor (allogeneic transplant), with the goal of restoring healthy blood cell production.
Underlying Causes and Risk Factors
The exact causes of most hematological malignancies remain unknown, but several factors increase an individual’s risk. Genetic mutations acquired during a person’s lifetime play a role in these cancers. These mutations affect genes that control cell growth and division, leading to uncontrolled proliferation of abnormal cells. Exposure to high levels of radiation, such as from atomic bomb survivors or certain medical treatments, is a known risk factor.
Certain chemicals, particularly benzene, are linked to an increased risk of some leukemias. Some viral infections, such as the Epstein-Barr virus, are associated with an increased risk of certain lymphomas, while the human T-cell leukemia virus type 1 (HTLV-1) is linked to a rare form of leukemia. A compromised immune system, due to inherited conditions, autoimmune diseases, or immunosuppressive medications, can also elevate the risk. Advancing age is another consistent risk factor, as the incidence of most hematological malignancies increases with age. Despite these identified risk factors, a precise cause for an individual’s cancer often cannot be determined.