Follicular lymphoma is a type of slow-growing non-Hodgkin lymphoma (NHL), which is a cancer that affects the lymphatic system. The lymphatic system is part of the immune system and consists of lymph vessels, lymph fluid, lymph nodes, bone marrow, the spleen, and lymphocytes. The two main types of lymphocytes are B-lymphocytes (B-cells), which produce antibodies to fight off infection, and T-lymphocytes (T-cells), which can destroy invading microorganisms or cancer cells. Follicular lymphoma is a cancer of the B-cells, in which the B-cells tend to form follicles (clusters) in the lymph nodes. As the cancerous B-cells spread, they cause lymph nodes to swell. Follicular lymphoma is categorized in stages I-V, depending on its severity and how many lymph nodes and other areas are affected. There are 3 types of follicular lymphoma: 1) transformed follicular lymphoma, in which the slow-growing cancer transforms into an aggressive diffuse B-cell lymphoma (DLBCL); 2) primary gastrointestinal follicular lymphoma, in which the cancer affects the small intestines; and 3) pediatric follicular lymphoma, in which the cancer is different in children than adults, remains in the area it first developed, and tends to be more benign.

In some individuals, follicular lymphoma may not cause any symptoms. Symptoms of follicular lymphoma may include persistent fatigue; fever; night sweats; unexplained weight loss; hard, painless, and swollen lymph nodes in neck, armpits, or groin; abdominal pain or swelling; enlarged spleen; chest pain; coughing; lightheadedness; headaches; paleness; bruising or bleeding easily; low levels of red blood cells, white blood cells, and platelets (cytopenia); anemia; and difficulty breathing. Symptoms of follicular lymphoma tends to come and go as relapses and remissions.

Treatment for follicular lymphoma depends on the stage of the disease and may require a multidisciplinary team of doctors and other specialists. Treatment for follicular lymphoma may include watching and waiting (for individuals with no symptoms), radiation therapy, immunotherapy, and chemotherapy. Individuals with advanced follicular lymphoma may be treated with anti-CD20 monoclonal antibody medications, such as rituximab (Rituxan) and obinutuzumab (Gazyva); chemotherapy regimens, such as bendamustine plus rituximab and CHOP-R (cyclophosphamide, doxorubicin hydrochloride, vincristine sulfate, and prednisone given along with rituximab); or rituximab with chlorambucil (Leukeran) or lenalidomide (Revlimid). Some individuals with follicular lymphoma may require maintenance therapy or medications for relapsed or refractory (resistant) lymphoma, such as idelalisib (Zydelig) or copanlisib (Zydelig), radioimmunotherapy combined with Ibritumomab tiuxetan (Zevalin), or Ibritumomab tiuxetan.