One of my patients asked me recently what lymphoma is. My knowledge of the subject was a bit dusty before I started researching this column. Medical knowledge of non-Hodgkin lymphoma has rapidly evolved over the last decade or so. It is a very interesting disease and a type of cancer that is illustrative of where cancer treatment in general is heading in the years to come.
“Lymphoma” is a broad term used to describe a large number of “lymphoid neoplasms.” A neoplasm is an abnormal growth of cells that can be benign (not usually dangerous to one’s health) or malignant (cancerous). Lymphoid neoplasms are composed of cells found in the lymph system. This system is responsible for filtering tissue fluid and killing foreign substances in our bodies, particularly infectious agents.
The lymph system contains two types of specialized cells that can kill or remove these foreign agents, either directly (T cells), or indirectly (B cells). B cells produce antibodies that bind to the foreign substances to assist in their removal from the body. When B and T cells multiply out of control, it results in different types of lymphomas.
The various types of lymphomas are named using a complex classification system based on cell morphology (what they look like) and lineage (their genetic makeup). Lymphomas are broadly classified into Hodgkin and non-Hodgkin lymphomas (NHL). Non-Hodgkin lymphoma is further divided into B-cell and T-cell types. B-cell lymphomas account for about 80% of NHL.
Medical oncology used to make a clear distinction between solid tumors (lymphomas) and tumors comprised of cells circulating in the blood stream (lymphoid leukemias). Now that we have more sophisticated testing methods, particularly genetic testing, it’s becoming more clear that these neoplasms can have both solid and circulating components. This makes it even more confusing to describe the multitude of lymphoma types.
Non-Hodgkin lymphomas are the seventh most common cancer and last year it was expected that about 77,000 new cases would be diagnosed which would have accounted for a little over 4% of all cancers. These lymphomas are about one and a half times more likely in men than women. NHL caused about 20,000 deaths last year. It is more common in Caucasians, and is usually diagnosed after age 50. The five-year survival of patients with NHL is about 73%.
Interestingly, specific types of NHL are more common in certain geographic areas around the world. A person’s lifetime risk of developing NHL currently is a little over 2%. However, the risk has been increasing about 3% a year over the last 40 years. This rise is likely due to improvements in diagnostic testing and new classification systems that include people who were previously felt to have benign disease. Our aging population, use of immunosuppressive drugs, transplant medicine and HIV infections have also been implicated in the increasing number of cases.
Most NHL is caused by the physical rearrangement of various parts of our chromosomes that contain our DNA. Certain occupations carry an increased risk of developing NHL. These include farming, pesticide application, flour milling, meat processing, painting, and those who work with rubber, plastics and other synthetics. Exposure to herbicides, solvents, petroleum products and organic chemicals like benzene & carbon tetrachloride (dry cleaning fluid) also increase one’s risk.
Symptoms of NHL can be highly variable. The most concerning, and those that often carry a poorer prognosis, include fevers, drenching night sweats, and weight loss. These are all termed “B symptoms.” Swollen lymph nodes (including the liver and spleen) are another ominous sign. Some people present with shortness of breath, chest pain, cough, and abdominal or bone pain.
The diagnosis of NHL usually involves blood tests, various radiologic imaging procedures (X-rays, CT scans, MRI, PET scans), and biopsies of suspicious lesions. It may also include examination of the bone marrow. Diagnosis and classification involves a lot of testing to identify the genetic signature to nail down the specific type of NHL. This makes NHL one of the leading examples of how genetic testing is being used in modern day cancer treatment. This is the future of medicine – determining the genetic makeup of cancer cells to try and determine what chemotherapy or biologic treatments will offer the best chance at remission or cure.