Cancer, lymphoma, non-Hodgkin: One of many types of cancer that starts in the lymphatic system that and does not look like Hodgkin's disease under the microscope. The most common symptom of non-Hodgkin lymphomas is a painless swelling in the lymph nodes in the neck, underarm, or groin. Non-Hodgkin lymphomas are diagnosed with a biopsy of an enlarged lymph node. Most are treated with chemotherapy and monoclonal antibody therapy either immediately in the more aggressive types, or at some point in the less aggressive or indolent types. Follow-up examinations are important after lymphoma treatment. Most relapses occur in the first 2 years after therapy.