According to MedlinePlus, lymphoma is a type of cancer that affects the lymphatic system, a key part of the immune system. There are numerous different types of lymphoma, but the majority of lymphomas are classified as non-Hodgkin lymphomas.
MedlinePlus states that non-Hodgkin lymphomas begin when an abnormal T cell or B cell forms in the body and propagates. As the cells divide, they can spread to virtually any part of the body. These cells are cancerous and cause symptoms such as fever, night sweats, fatigue, weight loss, coughing and pain. The cause of non-Hodgkin lymphomas is unknown, but people with compromised immune systems or certain types of infections are at higher risk.