Lymphoma is a group of cancers arising from lymphocytes, immune cells that normally help defend the body against infection. It commonly involves the lymphatic system, but can also develop in organs outside it. The two broad clinical categories are Hodgkin lymphoma and non-Hodgkin lymphoma. These categories contain distinct diseases rather than a single condition: their cellular origins, growth rates, symptoms, and responses to treatment vary considerably. (cancer.gov)
Cellular origins and classification
Lymphocytes belong to the immune system. Most non-Hodgkin lymphomas arise from B cells, while others originate in T cells or natural killer cells. Lymphoma can involve lymph nodes, the spleen, and bone marrow, as well as extranodal sites such as the gastrointestinal tract, skin, or brain. Classification incorporates the appearance of tumor cells, their immune markers, genetic characteristics, and clinical setting. (cancer.gov)
Hodgkin lymphoma includes classical Hodgkin lymphoma, characterized by Hodgkin and Reed–Sternberg cells in an accompanying population of other immune cells. Classical disease has four recognized histological subtypes: nodular sclerosis, mixed cellularity, lymphocyte-rich, and lymphocyte-depleted. Nodular lymphocyte-predominant disease differs in its pathological features and often has a slower clinical course. (cancer.gov)
Non-Hodgkin lymphoma encompasses numerous subtypes. Diffuse large B-cell lymphoma is a common aggressive form, whereas follicular lymphoma is generally indolent, or slow-growing. “Aggressive” and “indolent” describe disease behavior, not simply disease extent. Some indolent lymphomas can transform into more aggressive forms. (cancer.gov)
Biological changes and risk factors
Like other cancers, lymphomas develop through changes that disturb normal control of cellular growth and survival. Acquired mutations and other alterations in DNA can affect these processes. Molecular studies have identified genetically distinct groups within diffuse large B-cell lymphoma, helping explain differences in disease biology and treatment response. Such tumor changes do not necessarily indicate an inherited disorder. (cancer.gov)
Risk factors vary between subtypes. Older age is associated with many non-Hodgkin lymphomas, although lymphoma also occurs in children and younger adults. Immunodeficiency, HIV infection, and immune suppression after organ transplantation increase the risk of certain lymphomas. Some autoimmune diseases are also associated with increased risk. (cancer.org)
Specific infections are linked to particular forms. Epstein–Barr virus is associated with some Hodgkin and non-Hodgkin lymphomas; Helicobacter pylori infection is associated with gastric mucosa-associated lymphoid tissue lymphoma. These associations are subtype-specific, and infection does not mean that lymphoma will develop. Many affected individuals have no identifiable risk factor. (cancer.org)
Clinical presentation
A common presentation is painless enlargement of lymph nodes, often in the neck, armpit, or groin. Other manifestations include fatigue, itching, and symptoms caused by an enlarged spleen or a mass pressing on nearby structures. Disease in the chest may cause respiratory symptoms, while abdominal involvement may produce discomfort or swelling. (cancer.gov)
Unexplained fever, drenching night sweats, and significant unintentional weight loss are collectively termed B symptoms. They contribute to clinical assessment and, in Hodgkin lymphoma, staging designations. These symptoms are not specific to lymphoma: infections and other nonmalignant conditions can produce similar findings. (cancer.gov)
Diagnosis and staging
Definitive diagnosis usually depends on a biopsy of an affected lymph node or other tissue. An excisional biopsy removes an entire node, while a core biopsy retrieves tissue through a needle. Pathological examination evaluates both individual cells and tissue architecture; imaging or blood tests alone generally cannot establish the precise lymphoma subtype. (cancer.gov)
Laboratory techniques include immunohistochemistry and flow cytometry, which identify characteristic cellular markers using antibodies. Genetic testing can detect alterations useful for classification. Computed tomography and positron emission tomography, frequently combined as PET/CT, help assess disease distribution and treatment response. Bone marrow examination is used in selected circumstances. (cancer.org)
Many lymphomas use a four-stage anatomical framework. Stage I generally indicates one involved lymphatic region; stage II involves multiple regions on the same side of the diaphragm; stage III includes regions on both sides; and stage IV indicates disseminated involvement of extranodal organs. Stage is considered alongside subtype, tumor bulk, symptoms, and other clinical factors. (cancer.gov)
Treatment and disease course
Treatment is subtype-dependent. Established modalities include chemotherapy, radiation therapy, targeted medicines, and immunotherapy. Monoclonal antibodies are important in many B-cell lymphomas. Selected relapsed or refractory diseases may be treated with CAR T-cell therapy or hematopoietic stem cell transplantation. Some asymptomatic indolent lymphomas are managed initially with active surveillance rather than immediate treatment. (cancer.gov)
Many Hodgkin lymphomas and some aggressive non-Hodgkin lymphomas are potentially curable. Other forms may follow a prolonged course with repeated remissions and relapses. Prognosis depends on the specific disease, its extent, biological features, general health, and response to treatment. Long-term follow-up also addresses treatment-related effects, which can include organ damage and an increased risk of subsequent cancers. (cancer.gov)