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. At infection sites, large numbers of these microbial organisms collect in the regional lymph 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". In some areas of the body (such as the anterior part of the neck), they are often visible when swollen.
Lymphocytes recognize infectious organisms and abnormal cells and destroy them. There are two 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). Antibodies essentially alert other cells of the immune system to recognize and destroy these intruders, also known as pathogens (the process is known as humoral immunity).
- 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 (in the process of cell mediated immunity).
- 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 B or T cells or their subtypes.
- As the abnormal cells multiply, they may collect in one 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.
- 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 one of two major categories: Hodgkin's lymphoma (HL, previously called Hodgkin's disease) and all other lymphomas (non-Hodgkin's lymphomas or NHLs).
- These two types occur in the same places, may be associated with the same symptoms, and often have similar appearance on physical examination. However, they are readily distinguishable via microscopic examination.
- Hodgkin's 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 five subtypes of Hodgkin's disease and about 30 subtypes of non-Hodgkin's lymphoma.
- Because there are so many different subtypes of lymphoma, the classification of lymphomas is complicated (it includes both the microscopic appearance as well as genetic and molecular markers).
- 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 seventh most common cancer in adults and the third most common in children. Non-Hodgkin's lymphoma is far more common than Hodgkin's lymphoma.
- In the United States, about 66,000 new cases of NHL and 8,500 new cases of HL were expected to be diagnosed in 2010, and the overall incidence is increasing each year.
- About 20,000 deaths due to NHL were expected in 2010 as well as 1,300 deaths due to HL, 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's disease is most common in two age groups: young adults 16-34 years of age and in older people 55 years of age and older. Non-Hodgkin's lymphoma is more likely to occur in older people.
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:
- Unexplained weight loss.
- Night sweats.
- Lack of energy.
- Itching (up to 25% of patients develop this itch, most commonly in the lower extremity but it can occur anywhere, be local, or spreading over the whole body).
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 theflu 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.
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. In the 20-24-year age group, the incidence of lymphoma is 2.4 cases per 100,000 while it increases to 46 cases per 100,000 in the 60-64-year-old age group.
- Infection with HIV.
- Infection with Epstein-Barr virus (EBV), one of the etiologic factors inmononucleosis.
- Infection with Helicobacter pylori, a bacterium that lives in the digestive tract.
- Infection with hepatitis B or hepatitis C virus.
- Medical conditions that compromise the immune system.
- Autoimmune disease.
- Use of immune suppressive therapy (often used following organ transplant).
- Inherited immunodeficiency diseases (severe combined immunodeficiency, ataxia telangiectasia, among a host of others).
- Exposure to toxic chemicals.
- Farm work or an occupation with exposure to certain toxic chemicals such as pesticides, herbicides, or benzene and/or other solvents.
- Hair dye use has been linked to higher rates of lymphoma especially in patients who started to use the dyes before 1980.
- Genetics: Family history of lymphoma.
The presence of these risk factors does not mean a person will actually develop lymphoma. In fact, most people with one or several of these risk factors do not develop lymphoma.
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 andradiation therapy.
- Biological therapy, which takes advantage of the body's innate cancer-fighting ability, is used in some cases.
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.
- 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.