Lymphoma is a cancer of the lymphatic system that occurs when lymphocytes grow abnormally and accumulate in lymph nodes or other organs of the lymphatic system. The two main types are Hodgkin lymphoma and non-Hodgkin lymphoma. Risk factors include age, family history, immune system disorders, and certain infections. Signs and symptoms vary depending on the type but may include swelling of lymph nodes, fever, night sweats, and weight loss. Diagnosis involves biopsy and imaging tests. Treatment options include chemotherapy, radiation therapy, immunotherapy, and stem cell transplants.