Cancer is a complex, confusing, and ever-shifting field of medicine. While we know and understand more about the disease today than we did forty, twenty, even five years ago, there is still plenty that is not understood. As new insights come to light and disprove previously held theories, the definition of cancer changes.
Regarding the definition of lymphoma specifically, at its most fundamental it is a disease that originates in blood cells known as lymphocytes. Healthy lymphocytes traverse the body by way of the lymphatic system looking for foreign invaders such as bacteria, and their job is simple: kill them. In this way, lymphocytes work to keep us healthy and free of illness-causing pathogens.
The Lymphatic System
The lymphatic system is part of our immune system. It includes lymphocytes, a fluid called lymph, a network of fluid vessels, weigh-stations along the network known as nodes, and a handful of organs: notably the spleen, the thymus, the tonsils, and the bone marrow.
Cell Division and Apoptosis
Lymphocytes have a life cycle. They are born and they die. They also undergo cell division, a process wherein one cell divides into two daughter cells that are supposed to be identical to the original cell. Healthy cells are programmed to carry out certain functions, then begin a process called apoptosis, which results in the natural death of the cell.
However, the process of cell division is extraordinarily complicated, and sometimes, mistakes occur. Sometimes, these mistakes lead to the shutting down of certain cellular functions; in the case of cancer, the process of apoptosis is normally turned off, allowing for the cancerous cells to proliferate out of control in the body.
This proliferation is a very simple explanation of what happens in cancer. In lymphoma, cancerous lymphocytes proliferate instead of dying. For this reason, lymphoma is considered a lymphoproliferative disorder.
Compared to healthy lymphocytes, malignant lymphocytes are often large or misshapen. They have a tendency to accumulate at the lymph nodes, which causes the nodes to swell. The condition of swollen lymph nodes is called adenopathy.
However, cancerous lymphocytes do not always collect at the lymph nodes. The lymphatic system is great for fighting infections because it traverses the entire body, but it also means that if a cancer should develop in lymphocytes, it can start virtually anywhere in the body. Therefore, lymphomas are divided into nodal lymphomas—those originating and affecting a cluster of lymph nodes—and extranodal lymphomas—those originating and affecting regions of the body beyond the lymph nodes.
Lymphoma Definition: Subtypes
Lymphoma becomes extremely confusing when talk turns to subtypes of lymphoma, such as Hodgkin's lymphoma, non-Hodgkin's lymphoma, follicular lymphoma, diffuse large B-cell lymphoma, anaplastic large T-cell lymphoma, and many more. However, suffice to say that when lymphocytes become cancerous, they can become cancerous in dozens of different ways. When diagnosing lymphoma, a pathologist looks for certain identifiers and performs other lab techniques in order to determine which type of lymphoma.