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Lymphoma and Pets
Non-Hodgkin's Lymphoma 101
Every now and then a refresher is in order. Here we'll look at the very basics of the diseases known collectively as non-Hodgkin's lymphoma. Before getting started, lymphomas in general are said to be divided into Hodgkin's and non-Hodgkin's lymphoma.
However, a more accurate way of imagining this is to think of Hodgkin's merely as a very well-understood subtype of lymphoma. In an ideal world, the 'non-Hodgkin's' name would be dropped all together, and the 'Hodgkin's' name would simply become known as one of many diseases under the banner of lymphoma, since this nominal division reflects a very archaic understanding of the disease.
Non-Hodgkin's Lymphoma 101
When a healthy cell turns cancerous and forms a lesion or tumor or otherwise proliferates, the name and the type of that cancer depend on the kind of cell that has become cancerous (e.g., a haywire breast cell indicates breast cancer). Experienced pathologists can typically peer through a microscope at a given cancer cell and say, just by observation, what kind of cell it is.
So when a lymphocyte—a white blood cell—turns cancerous, it is lymphoma. All lymphomas are malignant diseases—meaning if left untreated, they will eventually kill the patient.
Lymphomas grow from a single lymphocyte that has mutated and survived and does not die when it is supposed to die. This ability to stay alive and proliferate is the definition of cancer.
Lymphomas are considered 'blood cancers,' along with leukemia and myeloma, because they don't form the same kinds of solid tumors as most other cancers.
Trying to stay on top of the classifying of the many subtypes of non-Hodgkin's lymphoma is a nightmare. Systems began to be created in the 1970s to try to categorize the emerging subtypes of the disease, and predictably, they began modestly: There were aggressive lymphomas, moderate lymphomas and indolent ones. Another decade meant another classification system, with grades (I through III) for aggressiveness as well as newly discovered subtypes of the disease.
Yet another decade arrived with a new system. What was three diseases had become a few dozen.
Today there are more than 100 different clinical entities that fall under the name non-Hodgkin's lymphoma. 'Different clinical entity' refers to individual cancers that can arise from a cancerous lymphocyte and that will be termed a lymphoma. Many have yet to be acknowledged by the World Health Organization as separate diseases, but it is likely only a matter of time.
Why is this happening?
New subtypes of non-Hodgkin's lymphoma are being identified quite often now, not because there is an outbreak of lymphomas but because the science of understanding the cancer cell has improved. As mentioned, cancer is still referred to by anatomy: breast cell = breast cancer.
However, even this classification is likely on its way out, as researchers begin looking at cancer from the molecular level: What are the specific changes to the cell's chromosomes that caused the cancer? The answer is important because those changes will dictate how and with what proteins the cell will communicate with other cells. These proteins are expressed on the cell surface, and they have become a common object of targeted treatment.
Treatment and Prognosis
Blood cancers have been the greatest benefactor of the last several decades of research, as survival rates for many types of lymphoma and leukemia have gone from close to 0% in some cases to almost 100% in others.
In the U.S. there are about 80,000 new lymphoma diagnoses made each year, according to the National Cancer Institute. On average, when the disease is found in early stages the 5-year survival rate is 82%. If the disease has spread only locally, the survival rate is 78%. In the case of advanced disease, the overall general survival rate is still relatively high at 62%. All of these figures will be different depending on the subtype of lymphoma.