Pathologist’s Corner – Dr. McIntire on Lymphoma
Published September 02, 2014 – Dr. Timothy McIntire
Lymphoma is a general term for a large group of blood cancers that affect white blood cells called lymphocytes. Healthy lymphocytes are important components of the immune system, as they help protect the body from disease caused by invasive organisms, such as viruses, fungi or bacteria. Lymphocytes recognize infectious organisms and abnormal cells and destroy them. 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.
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 over activity 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 tissues such as the spleen or the bone marrow. As the cells continue to multiply, they form a mass often referred to as a tumor. While lymphomas are often confined to lymph nodes, 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 70,800 new cases of NHL and 9,200 new cases of HL were expected to be diagnosed in 2014, and the overall incidence is increasing each year. About 19,000 deaths due to NHL were expected in 2014 as well as 1,200 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 may become 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, and 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)
If a person has swelling or symptoms, his or her health-care provider will ask many questions about the symptoms (when they began, recent illnesses, past or current medical problems, any medications, workplace, health history, family history, and habits and lifestyle). These questions are followed by a thorough examination.
If, after an initial interview and examination, the health-care provider suspects that a patient may have lymphoma, the patient will undergo a series of tests designed to provide further clarification. At some point in this workup, the patient will likely be referred to a specialist in blood diseases and cancer (hematologist/oncologist).
If there is a swelling (also called lump or mass), a sample of tissue from the swelling will be removed for examination by a pathologist. This is called a biopsy. A pathologist (a physician who specializes in diagnosing diseases by looking at cells and tissues) examines the tissue sample with a microscope. The pathologist’s report will specify whether the tissue is lymphoma and the type and subset of lymphoma.
Most of the time, an examination of the bone marrow is necessary to see if the bone marrow is affected by the lymphoma. This is done by collecting a biopsy of the bone marrow. Samples are taken, usually from pelvis bone. A pathologist examines the bone marrow under a microscope. Bone marrow containing certain types of abnormal B or T lymphocytes confirms lymphoma. Bone marrow biopsy can be an uncomfortable procedure, but it can usually be performed in a medical office. Most people receive pain medication prior to the procedure to make them more comfortable.
Regarding the treatment of 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.