What is lymphoma? In general, lymphoma is a type of cancer affecting cells of the lymph system. The lymph system is part of the immune system that consists of a network of lymph nodes, lymph vessels, and organs, including the thymus, spleen, and bone marrow. Lymphoma can arise from any of these tissues. There are two broad categories of lymphoma: non-Hodgkin lymphoma (NHL) and Hodgkin lymphoma, which is discussed in a separate article. The cancerous cell in NHL is called a "lymphocyte", which is a cell that ordinarily is involved in the immune response that protects the body from infection. In NHL, these lymphocytes divide at an abnormally fast rate causing enlargement of lymph nodes or other organs in the lymph system and are responsible for the symptoms experienced by children with NHL. Who is at risk for NHL? As for most childhood cancers, the majority of pediatric ... read more on Non-Hodgkin Lymphoma (Pediatric): The Basics