Lymphoma is a type of cancer involving cells of the immune system, called lymphocytes. Just as cancer represents many different diseases, lymphoma represents many different cancers of lymphocytes-about 35 different subtypes, in fact.
Lymphoma is a group of cancers that affect the cells that play a role in the immune system, and primarily represents cells involved in the lymphatic system of the body.
• The lymphatic system is part of the immune system. It consists of a network of vessels that carry a fluid called lymph, similar to the way that the network of blood vessels carry blood throughout the body. Lymph contains white blood cells called lymphocytes. Lymphocytes attack a variety of infectious agents as well as many cells in the precancerous stages of development.
• Lymph nodes are small collections of lymph tissue that occur throughout the body. The lymphatic system involves lymphatic channels that connect thousands of lymph nodes scattered throughout the body. Lymph flows through the lymph nodes, as well as through other lymphatic tissues including the spleen, the tonsils, the bone marrow, and the thymus gland.
• These lymph nodes filter the lymph, which may carry bacteria, viruses, or other microbes. The lymph nodes, or glands as they may be called, filter the lymph, which may on various occasions carry different microbial organisms. At infection sites, large numbers of these microbial organisms collect in the regional nodes and produce the swelling and tenderness typical of a localized infection. These enlarged and occasionally confluent collections of lymph nodes (so-called lymphadenopathy) are often referred to as "swollen glands."
Lymphocytes recognize pathogens (infections and abnormal cells) and destroy them. There are 2 major subtypes of lymphocytes: B lymphocytes and T lymphocytes, also referred to as B cells and T cells.
• B lymphocytes produce antibodies (proteins that circulate through the blood and lymph and attach to infectious organisms and abnormal cells). The combination attachment cell or antibody microbial organism essentially alerts other cells of the immune system recognize and destroy these intruders, also known as pathogens.
• T cells, when activated, can kill pathogens directly. T cells also play a part in the mechanisms of immune system control, to prevent the system from inappropriate overactivity or underactivity.
• After fighting off an invader, some of the B and T lymphocytes "remember" the invader and are prepared to fight it off if it returns.
Cancer occurs when normal cells undergo a transformation whereby they grow and multiply uncontrollably. Lymphoma is a malignant transformation of either lymphocytes B or T cells or their subtypes.
• As the abnormal cells multiply, they may collect in 1 or more lymph nodes or in other lymph tissues such as the spleen.
• As the cells continue to multiply, they form a mass often referred to as a tumor.
• Tumors often overwhelm surrounding tissues by invading their space, thereby depriving them of the necessary oxygen and nutrients needed to survive and function normally.
• Because of their uncontrolled growth, lymphomas can encroach on and/or invade neighboring tissues or distant organs.
• In lymphoma, abnormal lymphocytes travel from one lymph node to the next, and sometimes to remote organs, via the lymphatic system.
• While lymphomas are often confined to lymph nodes and other lymphatic tissue, they can spread to other types of tissue almost anywhere in the body. Lymphoma development outside of lymphatic tissue is called extranodal disease.
Lymphomas fall into 1 of 2 major categories. Hodgkin lymphoma (HL, previously called Hodgkin's disease) and all other lymphomas (non-Hodgkin lymphomas or NHLs).
• These 2 types occur in the same places, may be associated with the same symptoms, and often have similar gross physical characteristics. However, they are readily distinguishable via microscopic examination.
• Hodgkin disease develops from a specific abnormal B lymphocyte lineage. NHL may derive from either abnormal B or T cells and are distinguished by unique genetic markers.
• There are 5 subtypes of Hodgkin disease and about 30 subtypes of non-Hodgkin lymphoma.
• Because there are so many different subtypes of lymphoma, the classification of lymphomas is complicated and includes both the microscopic appearance and well-defined genetic and molecular rearrangements.
• Many of the NHL subtypes look similar, but they are functionally quite different and respond to different therapies with different probabilities of cure. HL subtypes are microscopically distinct, and typing is based upon the microscopic differences as well as extent of disease.
Lymphoma is the most common type of blood cancer in the United States. It is the sixth most common cancer in adults and the third most common in children. Non-Hodgkin lymphoma is far more common than Hodgkin disease.
• In the United States, about 54,000 new cases of NHL and 7000 new cases of HL were diagnosed in 2004, and the overall incidence is increasing.
• About 24,000 people die of NHL and 1400 of HL each year, with the survival rate of all but the most advanced cases of HL greater than that of other lymphomas.
• Lymphoma can occur at any age, including childhood. Hodgkin disease is most common in 2 age groups: young adults aged 16-34 years and in older people aged 55 years and older. Non-Hodgkin lymphoma is more likely to occur in older people.
CAUSES OF LYMPHOMAS
The exact causes of lymphoma are not known. Several factors have been linked to an increased risk of developing lymphoma, but it is unclear what role they play in the actual development of lymphoma. These risk factors include the following:
• Age: Generally the risk of NHL increases with advancing age. HL in the elderly is associated with a poorer prognosis than that observed in younger patients.
• Infections
o Infection with HIV
o Infection with human T-lymphocytic virus type 1 (HTLV-1)
o Infection with Epstein-Barr virus (EBV), one of the etiologic factors in mononucleosis
o Infection with Helicobacter pylori, a bacterium that lives in the digestive tract
o Infection with hepatitis B or hepatitis C virus
• Medical conditions that compromise the immune system
o HIV
o Autoimmune disease
o Diseases requiring immune suppressive therapy, often used following organ transplant
o Inherited immunodeficiency diseases (severe combined immunodeficiency, ataxia telangiectasia, among a host of others)
• Exposure to toxic chemicals
o Farm work or an occupation with exposure to certain toxic chemicals such as pesticides, herbicides, or benzene and/or other solvents
o Black hair dye, which for more than 20 years has been linked to higher rates of NHL
• Genetics: Family history of lymphoma
The presence of these risk factors does not mean a person will actually develop lymphoma
SIGNS AND SYMPTOMS
Often, the first sign of lymphoma is a painless swelling in the neck, under an arm, or in the groin.
• Lymph nodes or tissues elsewhere in the body may also swell. The spleen, for example, often becomes enlarged in lymphoma.
• The enlarged lymph node sometimes causes other symptoms by pressing against a vein or lymphatic vessel (swelling of an arm or leg), a nerve (pain, numbness, or tingling), or the stomach (early feeling of fullness).
• Enlargement of the spleen may cause abdominal pain or discomfort.
• Many people have no other symptoms.
Symptoms of lymphoma may include the following:
• Fevers
• Chills
• Unexplained weight loss
• Night sweats
• Lack of energy
• Itching
These symptoms are nonspecific. This means that they could be caused by any number of conditions unrelated to cancer. For instance, they could be signs of the flu or other viral infection, but in those cases, they would not last very long. In lymphoma, the symptoms persist over time and cannot be explained by an infection or another disease
TREATMENT
General health care providers rarely undertake the sole care of a cancer patient. The vast majority of cancer patients receive ongoing care from oncologists but may in fact be referred to more than one oncologist should there be any question about the disease. Patients are always encouraged to gain second opinions if the situation so warrants this approach.
• Although medical treatments are fairly standardized, not all physicians behave similarly.
• One may choose to speak with more than one oncologist to find the one with whom he or she feels most comfortable.
• In addition to one's primary care physician, family members or friends may offer information. Also, many communities, medical societies, and cancer centers offer telephone or Internet referral services.
Once one settles in with an oncologist, there is ample time to ask questions and discuss treatment regimens.
• The doctor will present each type of treatment, discuss the pros and cons, and make recommendations based on published treatment guidelines and his or her own experience.
• Treatment for lymphoma depends on the type and stage. Factors such as age, overall health, and whether one has already been treated for lymphoma before are included in the treatment decision-making process.
• The decision of which treatment to pursue is made with the doctor (with input from other members of the care team) and family members, but the decision is ultimately the patient's.
• Be certain to understand exactly what will be done and why, and what can be expected from these choices.
As in many cancers, lymphoma is most likely to be cured if it is diagnosed early and treated promptly.
• The most widely used therapies are combinations of chemotherapy and radiation therapy.
• Biological therapy, which takes advantage of the body's innate cancer-fighting ability, is used in some cases.
In addition to the oncologist, the medical team may include a specialist in radiation therapy (radiation oncologist), 1 or more nurses, a dietitian, a social worker, and other professionals as needed.
The goal of medical therapy in lymphoma is complete remission. This means that all signs of the disease have disappeared after treatment. Remission is not the same as cure. In remission, one may still have lymphoma cells in the body, but they are undetectable and cause no symptoms.
• When in remission, the lymphoma may come back. This is called recurrence.
• The duration of remission depends on the type, stage, and grade of the lymphoma. A remission may last a few months, a few years, or may continue throughout one's life. The latter is in all likelihood a cure.
• Remission that lasts a long time is called durable remission, and this is the goal of therapy.
• The duration of remission is a good indicator of the aggressiveness of the lymphoma and of the prognosis. A longer remission generally indicates a better prognosis.
Remission can also be partial. This means that the tumor shrinks after treatment to less than half its size before treatment.
The following terms are used to describe the lymphoma's response to treatment:
• Improvement: The lymphoma shrinks but is still greater than half its original size.
• Stable disease: The lymphoma stays the same.
• Progression: The lymphoma worsens during treatment.
• Refractory disease: The lymphoma is resistant to treatment.
The following terms to refer to therapy:
• Induction therapy is designed to induce a remission.
• If this treatment does not induce a complete remission, new or different therapy will be initiated. This is usually referred to as salvage therapy.
• Once in remission, one may be given yet another treatment to prevent recurrence. This is called maintenance therapy.
PREVENTION
There is no known way to prevent lymphoma. A standard recommendation is to avoid the known risk factors for the disease. However, some risk factors for lymphoma are unknown, and therefore impossible to avoid. Infection with viruses such as HIV, EBV, and hepatitis are risk factors that can be avoided with frequent hand washing, practicing safe sex, and by not sharing needles, razors, toothbrushes, and similar personal items that might be contaminated with infected blood or secretions.
